I bought some headlight cover restoration cleaner and polish for my daughter for Christmas and used it to restore her headlight covers. It worked great! Then I did our minivan's and my husband said it was noticeably better to drive at night now.
The amount of the cleaner needed is less than a teaspoon and I have a whole bottle. It takes less than 10 minutes to clean and polish the plastic, so it's quick and easy.
I am happy to share the bounty here and help you drive more safely with clearer lighting since we now have so much polish and very little need.
I have posted before and after pictures here, which are helpful, but don't capture the full upgrade. And, I posted a photo of the polish I used in case you would rather do your own. I bought this at Advance Auto for $10.