The must do is to tape off the stock right up to the butts edge with yellow masking tape,a couple thicknesses at least,to protect it from any kind of gouging.I spray a tiny amount of wd40 and rub it around the wood before applying the tape.This serves to keep the tape from pulling up any finish when you lastly remove it.
I do use a dremel rotary tool with sanding drum to grind down
pads and spacers real close to the tape,watching heel and toe angles as you go,then use 100 grit paper wrapped on a flat metal block,or fine file to just touch the tape,then switch over to 400 grit paper with a dab of wd40 to finish it off.The dremel sanding drum will like to dig into the rubber,but if you are steady and smooth with your passes it will cut it.It will also spew rubber grit evrywhere,so cover up-wear safety glasses etc.
Freezing the pad is supposed to be the trick,but I was always too impatient.
Cutting the butt to length I would use a fine mitre saw freehand, try my best to keep it straight and from both sides,over the tape to keep the wood from splintering out.
Use the sanding block to get the butt flat and square again,sometimes I would have to relieve the center of the buttface between the mounting screws in order to get it really flat when you check with a straight edge.
