The March Popular Mechanics has an article about restoring headlights to get the max light out of them. It works - photos attached.
The suggest a kit but I don't recommend it. The article has all the info you need and you can buy the stuff cheaper. 1st, call around to the local auto body and paint stores to see who sells sandpaper by the sheet. Some only sell it in packs. You need 1 sheet each of 1000, 1500, 2000, 2500, and 3000 grit. Then you need a small bottle of polishing compound. That's it.
I bought a kit by Permatex that was supposed to include sandpaper up to 2500 grit. However, it had 2 sheets of 1000 and no 2500 so I had to go hunting for the 2500. I found a paint store that had both 2500 and 3000 by the sheet for $1/sheet.
I have a grand total of 15 min. into this 1 headlight. You can see how much more light will get through this than the old, frosted one.
Let me know if you want more details on how to do it. It's very easy.
Dick
before: lights off and on
after, lights off and on: