ok wetsanding doesn't work. already tried that. laquer thinner should never be used on plastic
first i would try that mothers aluminum polish. its an old detailers trick. it takes a few times before it all clears up. it fills the scratches and repairs to new.
or i believe there is another product they sell in austrailia (i know i know) called "glass renew"
alot of the nissan cars, skyline R33's and nissan 240SX's with the bigger headlights had that fading issues with the headlights. i used to use this "glass renew" and mothers aluminum polish all the time to keep my headlights clear
EDIT: did some research and it wasn't mothers aluminum polish (which works but this works better)
Brasso metal polish
look here:
http://forums.nasioc.com/forums/arch...hp/t-3674.html
^^ that is the cheapest and best way i have found to restore headlights and foglights^^
i have also used this too:
http://www.headlightlenscleaner.com/index.htm