Removing white residue on rocker panels

[hpaddict]

Hi, I recently had to get a fender repainted on my 05 GT. I see some white, clay like spots/residue on the edges of the rocker panels (they're painted, not plastic). I've tried waxing and using mild scratch removers but to no avail. Any hints on how to remove it? Is it safe to use something like a 3M rubbing/polishing compound on a painted rocker panel? Anyone familiar with the automotive repainting process actually tell me what the residue is? It probably got there because the edges of the rocker panel weren't taped off that well...