There are two common types of whip finishers, the Matarelli and the Thompson. Most tiers prefer the Matarelli.
It is not right or wrong to use a tool or whip by hand. However, there is a right and wrong way to whip finish. Most fly tiers do not know that the direction of the whip finish is important. The goal is to get a tight whip finish with the thread wraps laid adjacent going toward
the hook eye.
Whip Finish direction (Amanda--) - The Fly Tying Bench - Fly Tying
As to whether to whip by hand or use a tool, use the method that is fastest and most accuratefor you
. Although I know how to hand whip finish, I can do that faster and easier with a tool than by hand so I use a Matarelli.
Charlie Craven uses the Matarelli to tie his two minute parachute adams AND he whips TOWARDS the hook eye.
You will see some well know fly tiers hand whip finish and others will use a tool. My friend, Gary Borger uses a Matarelli. Davie McPhail, one of the best fly tiers in the world uses a Matarelli whip finisher. He also lays a bit of head cement on the thread before the whip finish rather than afterwards.