On our late model stuff, we just use regular polish and get good results on taillites, headlites, marker lites, etc. I have tried some of the so-called plastic polishes and don't see any difference in the gloss.

If you really want the tailites to sparkle like new and to stay that way, spray them with catalized clear. We do that with headlites and taillites and they look great and the clear is much harder than the original plastic, so it resists new scratches and scuffs.

It is best to glass bead the surface so that the clear has a good textured surface to bite to. Sounds extreme, but works very well. We've done dozens, both older and newer.