There is a headlight cleaning/restoartion kit for $20 at wal-mart or any other auto place. Also, Krylon makes a clear coat spray the blocks UV rays. If you just wet sand it down you get rid of the buildup but are allowing uv to destroy the headlight again by entering through the lens, bouncing off the reflectors inside which then destroys all of the headlight.

 

This might sound stupid but if money is tight try toothpaste. It has grit to cut through the haze and a polish to shine it up.