I have taken this from a post that i had responded to asking about headlight haze.
I have had multiple success stories and no failures with this process. It takes time, but is far better than these junk kits they are trying to sell. What you are going to need is 800 grit sandpaper, 1,000 grit sandpaper, 2,000 grit sandpaper, a polisher that fits on a grinder, and plastic polish for a wheel buffer (it looks like a crayon). Take the headlamp assembly off of the car and clean thoroughly. Wet sand by hand with the 800 grit until the headlight's roughness has gone away (about an hour). Then move on to the 1,000 grit and wet sand it until it is smooth and does not catch anything on your skin when you move your hand across it (about 30 to 45 minutes). If anything catches, wet sand again with the 800 grit. If needed, sand again with the 1,000 grit. Then wet sand with the 2,000 grit until it feels as smooth as a baby's ass (about 1 hour). Careful attention must be adhered to to make sure you do not burn the plastic and waste time sanding more or ruining your headlight. Attach the polisher to the grinder. Make sure the grinder is secured. Turn on the angle grinder. Apply the polish to the buffer until it seems as if it has covered the contact point of the polisher. Take the headlamp assembly and starting from the left to the right (or vice versa) press the headlamp lens against the polisher until you get the results you want. Make sure you keep moving the headlamp assembly at all times or you may burn the headlamp lens. Make sure that the polish is always coated on the polisher. When you believe that you have a clear lens, wipe off the excess polish on the headlamp lens. Repeat this step over until you have achieved the desired results. This does make a mess but will show that doing it this way will save you from buying new headlamps and last about 5 years (My fathers 2000 camaro headlamp lenses just started to fog up again after I did this exact process to them in 2005. I will be doing this process to my 04 LS also. It took me about an average of 4 hours for each headlamp to be done correctly. The same can be done for the fog lights.