I've found that a thumbnail works reasonably well on the cured stuff. Uncured? I'd wipe as much as possible off, then use mineral spirits or denatured alcohol to remove the residue. Alternately, wipe off as much as possible then use your thumbnail or a piece of Gorilla tape to remove whatever is left over once it cures.Is there a safe solvent that can be used to remove uncured Proseal from plexiglass?