Went after my old headlights with some wet/dry sandpaper and a bit of polishing compound.

I can see into the light more clearly,
but I'm not sure how much more light is coming out when they're on.

Might go after them a little bit more.
Unfortunately they're old enough the plastic itself is a tad crazed;
the damage is not just on the surface.

Smoooooth to touch, though.