i had the same problem when i unbolted mine. i couldn't get a lot of the residue off. needless to say i took her to the body shop and had the holes filled and painted over...
^^ it shouldnt, paints clear is urethane you should be able to laquer thinner the shit out of with out doing anything to it. the underside of the decklid is a different story tho, that paint will come right off.
i did the 2000 grit too. i ended up putting the wing back on till i can get the holes filled and painted. those plugs even painted look bad and i ended up getting the question "why did you take the wing off?" all the time.