What kind do you have?
There are essentially two different designs, the Materelli Style with an oddly shaped bent wire with a sharp hook which rotates within the handle or the Thompson Style that has two thin springy wire arms, one of which that may or may not rotate.
If you have a Materelli style or the Thomson style that rotates, the trick is to use a finger to keep it from rotating while you are hooking the thread and to TRIANGULATE the thread before wrapping.
If you have a Thompson style that doesn't rotate and you have mastered it, you will quickly figure out how to do a whip finish with just two fingers. While I can do it, I always use one of my Materelli whip finishers which are the real deal and unfortunately no longer available.
While the knock-offs are OK, the real Materelli has a few design elements that I like better, maybe because I have been using mine for eons as well as the other tools Frank Materelli made like the best steel tube bobbin ever.
As far as turns go, maybe four at most on bigger flies and less on tiny stuff. A common mistake among beginners is too many thread wraps in general on everything.