I had the foggy hazy headlights. They felt rough and crackled. I found the 3M Headlight restoration kit and they look like new now. This was for the outside though, not inside.

Not bad for $20 kit and 2 hours of time. Pickup up kit at Autozone but saw it at Walmart too.

Here's a link to the kit and video by 3M: Restoring a Headlight 3M

Here's some before and after photos. The overcast day put a grainy look to the after shots but they're shiny and way better than before!