[roncor]

Here's a variety of specialized products designed just for headlights. I'm sure most of them would work for what you need. Check them out here:

Headlight Lens Care: Polish out scratches & haze to restore clear plastic headlight lens covers. Wolfgang, Meguiars, Plexus, lens cleaning system,

And, a guide "how to" do it yourself:Wolfgang Headlight Lens/ Clear Plastic Restoration Guide