Steve Voigt
As someone who used the "scary sharp" (a terrible name btw) method way back when, my advice is to throw it in the trash and buy some sharpening stones.
OK, I suppose that's a little harsh; there is a place for sandpaper, e.g. flattening the backs of vintage irons or freshly heat treated new ones. In that case, I agree with the suggestion to use mineral spirits to loosen the paper, especially if it's been there a while.
But for day to day sharpening, virtually any type of stones will be an improvement.