I use the same polish/wax/sealant on my headlight (covers) that I do on the paint. It's strong enough to remove road film & gunk, but no so strong as to damage the plastic or plastic coating. And the wax/sealant adds protection. It also helps to see better at night in the rain by letting the water bead up and roll off instead of building up and distorting the light - try driving in the rain without your wipers sometime WITHOUT any windshield coating and see what happens. You vision through the glass will be severely distorted, just like the light trying to get through unwaxed/coated headlights.