The teeth tool doesn't work for me either. I used a heat gun to soften
the paint then a 4" scraper with sharp edge to remove the wallpaper
underneath (top layer of the paper). It comes right off. Then using
hot water and a sponge, wet the underlying brown part of the wallpaper.
Use same scraper to get it off. Then I clean the residue with a
cleaner called Awesome that I get at the dollar store. Then it's ready
to spackle.