The true rotary vice can be used for specific Tie Betterniques in several ways. But before I address those I will make some general considerations on using rotation.
One thing you have to consider when rotating the vice is that thread and material is either wound on or off the hook when the vice is turned.
This means that you often have to add turns of thread before rotating or remove them afterwards. Failing to do so can either loosen previously tied in material or add extra, useless turns of thread.
You are adviced always to add or remove the same number of turns as the number of revolutions you want to turn the vice.
If you are a right hand tyer winding the thread clockwise (when seen from the hook eye) you can use the following guidelines. If you tie with the left hand or counterclockwise you will have to deduct your own.If you want to rotate the fly 'towards yourself' - that is counterclockwise - you can remove the same number of turns of thread after you stopped turning.
These rules only apply for several full turns of the fly in the same direction. If you are just inpsecting the fly, it's more convenient to turn it over and the back again the opposite way, thus removing the single or few extra turns.
You can also use a bobbin holder to completely avoid this.
Rotating and the bobbin cradle
The right bobbin cradle - here shown on a Waldron vice - can keep the thread from winding on or off the hook shank when rotating the vice.
If you use a bobbin cradle on your vice, you can almost completely avoid the problems with adding and removing turns of thread when rotating the vice.
Most bobbin cradles will hold the thread horizontally away from your fly in front of the hook eye, thus making it parallel to the hook shank. As the thread will often be 'caught' by the eye and stay fixed there, you can just spin away without having the thread wind on or off the shank. And not only will it keep the thread from wrapping, but - of course - also keep it out of the way when you apply material to the shank using the rotation technique.
The thread might get twisted a bit, but that is easily overcome by untwisting the thread in the usual manner.
It's obvious to use the rotation for applying dubbing on the fly. I only rarely use the method as I usually rely on twisting the dubbing for a looser or tighter body, but it can be handy and will in some cases be a good solution for an even body.
Good examples for the use is when you wind on dubbing ropes, where the dubbing material is tightly spun on the thread and you want an evenly segmented body. Other cases could be when the body is made from 'compound' dubbing put together from several materials like dubbing and tinsel or dubbing and ostritch herl. All these combinations can give some very fine results, but only look good when the material is evenly twisted along the hook shank.
When applying dubbing the thread will usually be the 'carrier' and will not need to be out of the way. Just twist the dubbing on the thread and start winding the dubbing on the hook shank by rotating the vice counterclockwise. When you are satisfied you just tie on as you usually would.
If you use a dubbing loop and a dubbing twister, you will need to handle the thread as described above. Make a loop and bring the thread forward. Add the dubbing, twist it and rotate the rope on the hook shank by rotating counterclockwise. Tie off and cut off surplus. You don't need to remove the dubbing twister or use a hackle plier.
Adding body material
This is a good method when it's very important that a material does not become twisted and that particular material isn't easily kept straight. I rarely use this technique for anything but larva lace and body glass - like on the Crazy Dane. I do not use it for mylar tinsel and other materials that are easily controlled when wound in the normal 'overhand manner'.
Tie in the material as you usually do and wind the thread to where the material will be tied down. If you want to use a bobbin cradle to hold the thread while rotating, you will have to wind the material towards the hook eye, thus keeping the thread in front of the material near the eye.
Decide what way you want your material wound. The 'normal' clockwise way will mean rotating the vice counterclockwise - towards yourself - and vice versa.
When the material is safely attatched and the thread out of the way, grab the material with your right hand close to the fly, and start rotating the vice in the desired direction with your left hand.
Let the right hand follow the hook shank in the direction that the material is applied, and either hold the material tight or let it slip slowly between your fingers. The first method is likely to give a more even body.
When there's enough material on the shank, you shift it over to the left hand, hold it tight, release the bobbin holder and and unwind the thread to the tie off point of the material. Here you tie the material down and cut it according to the pattern.
Adding a hackle
Palmering a fly can be very easy using a rotary vice. Once you have tied in tha tip or butt of the hackle, you simply grab it close to the fly, and let it slip through your fingers while turning the vice in the desired direction. You can even - by positioning your fingers properly - stroke back the barbs on one side of the stem. If the feather is of a good quality and has been tied in properly it will behave perfectly. If it's a poor quality feather or has been tied in at the wrong angle with regard to the direction of the hackle, it is likely to twist at a certain point and leave you with a fuzzy looking hackle.
I personally still prefer to wind my palmer hackles in the traditional way, but for fast tying the rotation can be a great help.
Adding ribbing material
Also for fast tying the rotation can be a blessing when you wind ribbing. On a tinsel body I usually prefer doing it carefully in the traditional manner, but on dubbed bodies and over palmer and body hackles I usually use the rotation.
After the hackle has been wound and secured - either with tying thread or the first round of tinsel, you grab the tinsel with the right hand and start rotating the vice with the left. I normally wind the ribbing in the opposite direction of the body material or hackle. In order to avoid catching the hackle fibers under the ribbing I wiggle the ribbing material from side to side while I rotate the hook. This will stroke the fibers aside and normally make the ribbing find its way between the fibers, catching very few. I wind the rib in one continous movement, but if I see fibers getting caught or the ribbing becoming uneven, I just reverse one round and continue from there. It's a fast and convenient method and for flies with 'rough' bodies; yarn, dubbing etc. I can't see the difference between flies made this way and with the traditional method.
Most people will varnish their flies from above, which can be fine, but also frustrating. Often the varnish will be difficult to distribute on all sides of the head of the fly. One place seems to have a magic attraction though, and that is the eye. By using the rotation you can not only get an even and smooth head, but also avoid the varnish in the eyes of the fly.
The varnish will simply follow the laws of physichs and fill the gaps when you add it using a bodkin or a needle. These gaps will include the angle between the head and the eye... and the hole in the eye. This applies to all types of eyes: down, ring and up. As soon as the drop touches both sides of the eye, nature will play its trick and try to close that gap. The surface tension of the varnish will do the job nicely (left illustration 1 & 2).
Adding varnish the traditional way risking the hook eye filled (above) and with a rotary vice where the varnish settles in the gap between the tapered head and the hook eye.(right)
So what you need to to is avoid exposing both sides of the hole to the varnish. This can be done by being very careful with the needle and using small quantities of varnish. But the easiest way to do it is by turning the hook 90 degrees. This will leave the eye in a vertical position, and make it almost impossible to strike both sides with the drop of varnish. Any varnish spilled towards the eye will just fill the steep angle between the eye and the head - and not enter the eye (right illustration 1 & 2).
After one side you turn the hook over 180 degrees and do the same for the opposite side (right illustration 3). Now you can carefully smear the varnish over the whole surface of the head while rotating the fly slowly. You can even add more varnish, because now the laws of physics work for you. The surface tension of the already applied varnish will hold on new varnish added and actually make it more difficult to have 'stray varnish' enter places where you do not want it.
If you like really fat heads you can add lots of varnish and turn the fly slowly while it dries or you can add varnish more modestly, but turn the fly upside down while it dries in order to have a more smooth and rounded upper side of the head.
Trimming deer hair
When tying muddlers, bass bugs or other types of spun deer hair flies, the rotation of the vice can be used in the final trimming process.
I use a pair of serrated scissors or - sometimes - a razor blade. I hold the scissors or blade in an angle that is comfortable and gives a good view of the work in process, which for me is with the surface to be trimmed facing upwards and a little away from myself, enabling me to see the fly in profile and still see the work in progress 'under' the tool.
I trim the underside first by rotating the finished, varnished and dry fly to face hook point up and slightly away from myself. I cut once and tip it over 90 degrees, cut again, tip back 180 degrees and cut once again. This takes care of the underside and sides of the fly. Now I turn the fly to its upright position and trim the top.
This leaves me with a very rough fly. I assess my work and start trimming closer. I keep the scissors in the angle that is most comfortable and rotate the fly to meet it. The last part of the trimming is done by constantly rotating the fly in small increments and constantly snipping very little hair away.
I used to do this while holding the fly in my left hand turning it while trimming, but the rotary vice gives me much more control and precision.