The best cutting method I've found is to hold a 4" scraper hard against the
edge you want to retain and use a cheap, soft steel, pen knife that you can
sharpen every few minutes on sandpaper. The Opinel curved blade is ideal.
A lot of the trouble with papering could be overcome if you could cut a
straight line to join up with a fresh edge. Overlapping and cutting through
both works sometimes but usually one side or the other tears.
Peel back and scissors doesn't work well for me because I can never see the
bloody mark I'm supposed to be following properly.