Restoring Your Dingy Yellow Headlights. Does It Work? Check Mine Out!
Last year I used Maguire's brand headlamp restore system. It was almost $30 (might be cheaper now) and a year later they were dingy again. I think that's gonna happen no matter what you use.
This year I bought the 3M brand. It's a little more dangerous because there's no hand-sanding with this one. It's all power drill and you have to be careful not to "catch an edge." I did mark mine a little, but the difference is still huge and not that noticeable all in all.