Simple method for regaining crystal-clear headlight lenses:

1. Wet sand with 600 grit paper.
2. Rinse.
3. Wet sand with 1000 grit paper.
4. Rinse.
5. Wet sand with 1500 grit paper.
6. Rinse.
7. Wet sand with 2000 grit paper.
8. Rinse.
9. Hit them with Turtle Wax Rubbing Compound.
10. Rinse
11. Hit them with Turtle Wax Polishing Compound.
12. Rinse.
13. Dry.
14. Wax the lights with plain Turtle Wax.

My experience? Great! Went from almost brown headlight lenses to crystal clear in under an hour. I used to have pics up, and I would have to find them again to show the evidence. I would definitely do this again, as all the materials ran under $20, and can be used as many times as needed during the life of the vehicle. Compared to $600 for new headlight assemblies, this option was a no-brainer. Since I waxed them monthly afterward, they never yellowed again... Even in the Florida sun!

Hope this helps (even though not in an actual write-up format)!