Worse comes to worse... ive sprayed plastic lenses before with tinted clearcoat.... hey it makes the scratches disappear. ive put a few drops of black into clearcoat and sprayed it on taillights to tint them. thats if all else fails though. you would have to sand it again though with like 600 - 1000 grit paper then do that. id really try to get all the scratches out first though. still compound and polish and repeat. for now thats really all i can saythat should work. its kind if a pain to polish plastic by hand but its really the only way to make sure they wont melt.