What have you found to be the best method for getting rid of build-up residue in the front headlamps in 99-04 Mustangs?

 

new ones

I've wet sanded the lenses before but they'll get ugly again in a few months unless you clear coat em.

 

what he said

 

Mined looked awful when i bought the car in the beginning of june, so i wedsanded from 320grit all the way to 2000 grit (use the 320 for a good while to make sure you get ALL of the residue off) , then topped it off with a buffer and some rubbing compound (beware of swirlmarks!!!). then i waxed and buffed them up really nice, only prob was the the driver side headlight had a pretty big crack from a rock to begin with, it took a long time but i notice that the more time you put into cleaning it, the better it will be in the long run, this is my 3rd car having to wetsand the headlights and by far the stangs lights look the best.... if you clean them and wax them oh, once a week, they will shine for a good long while... mine still look good!