my buddy had a lot of overspray on his wheels that he kept on there for 3 years and last week end we clay bared them and it came right off without damaging the shine of the lip.

never dull might work but theres a lot of labor using that bc your polishing the lips. but to just removed the overspray claybar will remove them with very little labor.

i dont know about the fix a flat, is it very thick? if so just take a brand new razor blade and start cutting away little pieces remembering not to hit the wheels with the blade and then claybar the rest.