which stuff are you referring to??? Lifeseal will come off with some moderate pressure using a terry cloth and some spraynine or greezoff, worst case some acetone. 5200 comes off with the release agent but it doesn't penetrate well so if you have it on say a trim tab, good luck! Had someone put on an outboard brakcket with 5200 once and we lifted the entire boat by the bracket and it didn't come off... 4 guys jumping on the back finally ripped it off and took all the gelcoat with it.