My rear spoiler has the common problem where the rubber has deteriorated some, so that part of the upper surface still has some gloss on it and part of it is dull (micro-cracks). It has bugged me for a while, have even thought of replacing it. But paint is fine, new spoilers are apparently NLA, and most used ones will have a similar problem. Anyway, I simply took some 220 grit sandpaper and sanded the glossy areas, then wet sanded with real fine stuff all over (RUBBER ONLY - watch out for the paint!!) Took about 10 minutes, now has a uniform dull appearance which looks great, esp when you put a little protectant on it. FWIW.