Use regular toothpaste and a small buffer. No product will ever get back to 100%. The plastic itself is deteriorating. The exposed surface suffers the worst from sunburn, UV and Ozone in the air. All plastic does. And, eventually the entire lens will yellow and become brittle.  The DOT should have never allowed this crap for headlights.

Wow, he really wanted clear lenses, another half an hour of taking stuff off and and he could have changed the heater core!