I try to keep it simple...

Clip board to 'hold' the skin...

Metal straight edge ruler for a guide...

Single edge razor blade...

The 'trick' if there is one, was shown to me by a friend that runs a leather store (he makes some incredible things with leather, AND he's a fly fisherman too!) You don't want to cut all the way through the hide...score it most of the way through, then tear the piece from the hide...no lost hair...much less mess...does take some practice/skill to get it right.

I can cut an entire skin into strips in about five minutes this way.

Buddy