The one thing you absolutely need to know if you have tied in the thread and started on your fly is also
how to finish the fly. At some point the thread has to be cut and obviously the stuff you've been tying
in has to stay on the hook. There are a
few different methods to do that. Some do it with a few half-hitches and a drop of head cement. Some do
it by doing the last few wraps with a little super-glue on the thread. But the method used by most is
undoubtedly the whip-finish knot.
The whip-finish is a tie-off version of the normal thread mount method. Just like the first few wraps
lock the tag end to the hook when you start to tie the fly, the last few wraps will lock the tag end
when the fly is finished. The difference - at the tie-off, the bobbin end will represent the positioned
tag end and wrapping has to be done differently.
There are two basic types of tools for this. One has several
different models which can go under many names, such as 'Simple', 'Standard', 'Thompson', 'English' and
'Classic'. They can look a little bit different from eachother, but the technique for using them is
pretty much the same. The other is mostly refered to as the 'Matarelli' type. The biggest difference
between the types, aside of the design, is that the 'Standard' type has a fixed handle and has to be
rotated by the tier TO wrap the thread, while the Matarelli model instead rotates freely inside the
handle and will follow AS the thread is wrapped. It's a "speedy" for sure.
Then there is of course the finger whip-finish. It's probably not as fast as the other two, but instead
it does save you the time it takes to find the tool deeply buried in stuff on the bench. It also offers
a lot more in range than the tools do. With your fingers, you can keep a wide loop and easily tie off
far back on a big fly, still avoiding obstacles like wings and hackles etc. in front of it. There is no
reason to not learn the finger whip-finish, just because you have got and master the tool.