There is a product,,, comes in a silver package,,, called "Crystal View" it is available at most large parts stores,,, basically it has two wet sanding pads,, a buffing pad, a polishing compound and a sealer. It works great,, you wet sand with rougher grit, move on to finer, move on to polishing compound, finally seal. Entire process took me about 30 mins to do my right lens,, looks new. (left was replaced after an accident, and difference in the new and old I had to do something).
Web site says it takes 5 min,,,, I really took my time in doing mine.
Here is a link.
bestheadlightcleaner.com
Tom