I just did some VW Beetle headlights that were the worst i have ever seen, you couldn't even see the reflector.
The car failed inspection before i got it for these, at over $700 a pair for OE it was time to experiment. There was nothing to loose at this point, it either comes out okay or it gets aftermarket junk (the worst option IMHO).
This was done with the lights removed from the car. I used the common stuff almost everyone has at hand or is inexpensive.
I used a 4" square oscillating sander, a 6"x4" could also be used, loaded with 2000 wet/dry.
*Wash the lens in the sink (i used a big shop sink) with warm water and Dawn, rinse and leave wet.
*Smear a little Dawn on the wet lens and start using the sander on it, throw a little water on the lens if it gets dry. Keep the tool moving and the lens wet.
*Continue until the lens is a uniform haze and looks nice and clear when wet with water.
The next step use a round 5 inch orbital sander with a couple of cheap HF hook and loop pads. One orange and a black.
No need for a dedicated polisher or high dollar pads, these are cheap enough to throw away after.
*Put the pad on the round sander, damp the pad with a spray bottle and spear some rubbing compound on the lens.
*Polish the lens, stop when the compound begins to go dry, wet the lens with more compound and water.
*Continue until lens is clear, it will still have a haze from compound.
*Switch to the black pad and use a plastic polish, polish until the lens looks like glass (it will).
*Wash the lens again with dawn and water thoroughly then rinse and dry.
You will need a spray can of U-POL UV resistant clear.
*Mask off anything you don't want sprayed, wipe the lens with a tack cloth or microfiber. Never use red shop rags they contain silicone.
*Spray one thin coat, wait 10 min then another thin to medium coat. do not spray this too heavy it can go off color.
*Let dry at least 5 hrs before handling.
Note.
Use a plastic polish like Novus 2 that does not contain protectants like the Meguiar's G12310 PlastX that will prevent the clear from adhering properly and may cause fish eyes.
http://www.amazon.com/U-Pol-Products-0796-Clear-CLEAR/dp/B009LHER0M
http://www.amazon.com/NOVUS-Plastic-Fine...+plastic+polish
http://www.amazon.com/3M-03900-Rubbing-C...ubbing+compound
The VW lights came out like brand spanking new, absolutely crystal clear. The clear will protect them for years. It is made for this job.
For sanding i only used 2000 wet and dry, Dawn and water, nothing else. Let the machines do the work.