this happened to me with my G's headlights.
I just went ahead and bought another set of used headlights.
Spraying clear sounds like your best bet. Id have the body shop spray the clear though. Im sure they have some professional grade stuff that should keep up with the sunlight/heat factor

_M

 

another quick fix that does a pretty good job is crystal view. I failed the same way as you on my previous car, and while i was searching for some new headlights I came across this stuff and it works GREAT! You should be able to pick this stuff up at Autozone for like $20.. it comes in a kit and leaves a clear layer you apply to the outside lens and clears it up really well. I know this site's kinda tacky but you get the idea.. http://www.myheadlight.com/

 

did the clear coat and it didnt seem to work well remember i got to spray the inside and out side of lenses
thanks.

 

i would probably have to buy 4 kits sense i f*up both sides.

 

so its been a wile and tried lots of methods..i decided to re- sand them all over and ive been buff/polishing with plastX and 3m rubbing compound for the past days,they look pretty good and pretty clear..the only thing is when i pic them up and look at them directly in the sun light you can see all the scratches . i dont like that but i decided to get them the best i can and put them all together and just let it be...
i will see how well they hold up and i will deff get new head lights in the future.