Years ago when I rented out my home, the tenant stuck on no-skid decals on the bottom of my bathtub. (Ceramic bathtub installed in 1948.) I removed the decals as best I could, but there are still rough spots in the tub that also catch dirt, residue from the stick-um on the decals.

Is there a way to remove this residue? (I'm not interested in tearing out the tub, which would mean having to remodel every part of the bathroom. The bathroom is now only used for guests.)