This is a method that I got from someone from another car related forum. Supposedly the UV protector is the same as what companies are selling for alot of money, but you can run down to home depot/hardware store to pick up everything you need for about $20-$25.
My process is basically already well known:
Wetsand-400, 800, 1000, 1500 and 2000
Buff-System one polish or equivalent with a high speed drill with small wool pad attachment
But here is the "new" part......
UV Sealer-Helmsman Spar Urethane(Indoor/Outdoor)Clear Gloss mixed with Mineral Spirits(1part urethane to 1 part mineral spirits.
After you buff the lights out with your polisher, you wipe down the headlight with denatured alcohol or isopropyl alcohol (to eliminate any compound residue.
Mix the urethane and mineral spirits in a plastic disposable cup. Remember the dilution ration- 1 part to 1 part.
Then, take a blue 'scott' shop rag and fold it up into a 1 inch x 1 inch square. Then dip the rag into the mixture and wipe it on the headlight. Dont use too much or it might run, but start at the top of the light and work side to side. It took me a few times to get my method down, so if you mess up with application, wipe it off with mineral spirits and start over.
This UV sealant dries in 10-20 mins usually and is far superior to any average detail product(paint sealant, wax etc.......)
Its like a clear cote, but you dont spray it, not as messy.
Longevity-The original "creator" of this method told me that he did a headlight restoration with this method about 2 years ago for a customer, and he said it still looks good.
End story. I used some of my birthday money to get the materials and when I get my car back, this will be my new project.