Originally Posted by Mike-in-Orange

The trick to restoring headlights via sanding is to refine the sanding marks as much as you can before buffing them out. Meguiar's Heavy Duty Headlight Restoration Kit comes with 1000 grit and 3000 grit sanding discs, and that 3000 grit is key before using the supplied wool buffing pad on a good plug in drill.

If you have a buffer already you can skip the kit and just buy the abrasive media you need. Depending on how bad the headlights are you'll want to start with at least 1000 grit wet, or as coarse as 320 grit dry. The 320 grit is for extremely oxidized and yellowed lenses, but it's amazing how far gone these can be and still be brought back to crystal clarity. No matter how coarse you start with, always refine those sanding marks down to 3000 grit or thereabouts. The resulting sanding mark will be very light, very predictable, and very easy to buff out. If you have a DA buffer you can mount a smaller backing plate and 4" foam pads to it, and use some Meguiar's M105 from our pro line, or even Ultimate Compound from our consumer line to buff out the sanding marks. Piece of cake! You can then apply a sealer of some sort, or just a good coat of wax.