I use power scissors on mine, the razor blade trick didn't work. Skill makes a power shear with a rotary blade for cutting leather and that's what I use. Cut the sides first in about 1/4" strips working from the outside edge toward the center of the back. You will reach a point where the hide will get super thick and extremely hard to cut, that's usually where I stop with it. I have used that thicker part for silencers, but you have to thin the hide down on a belt sander until it's thin enough to be pliable so you can wrap it around the string.
I've been selling my own beaver silencers for over a year now. I'm out of tanned beaver at the moment. You will find out that those silencers are tough as nails. I get alot of repeat customers for these silencers, but not because they wear them out. Normally it's when they buy a new bow.
Good luck with it and if you need help just shoot me a PM.