Just wanted to share my experience with a 3M "Lens Renewal System" aka headlight polish/cleaner. I'm sure there other products out there but this worked very well.
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The actual headlight looked worse than on the before picture, very yellowish.
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Take your time, read the instructions AND follow them.
Don't rush and try to do all the lights with just one set. If the lights are very yellow, use a second set.
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Again, the after picture doesn't do justice of the real condition. The headlights look as good as new!! Took me about 45min per side. Well worth for the looks and better light output.
Hope this info helped.
dc
PS: Double tape the area around the lights, in particular corners and edges!!