I don't waste a lot of time on this job, to get them like brand new (seriously, not close but new) in a few min here is how i do it.
Mask off the light well with 3-4 layers of tape or remove it, Sand with an orbital sander and a foam 3000 grit foam disc. These come in 6 inch so use a old 5 inch disc and mark the pad then cut it down to use on the common 5 inch orbital sanders.
Dip the pad in a shallow pan of water so the pad holds water and stays wet, sand it till it looks perfect.
Polish it with compound and swirl remover after sanding using a buffer, i use a 6 inch rotary, the orbitals are painfully slow. Do not skip this step, it makes the difference between looking good and looking new!
Wipe 2X with alcohol, let dry and blow a couple of coats of clear on it. I use 2K when i paint something else but U-POL has a nice UV resistant rattle can clear. The picture is all reflections but it is 100% crystal clear.
You can 3000 sand the clear and buff it again but you don't have to.
This one was pretty hazed, 10 min per light total prep time.
You can buy the these product single at an auto body supply store. The disc are abut $3ea
http://www.amazon.com/Meguiars-S6F3000-Professional-Unigrit-Finishing/dp/B004QJIY36
http://www.amazon.com/U-Pol-Products-079...=U-POL+UV+clear