this is why you are struggling and causing hot spots/damage to the light
Ignore 3m, loads of clean soapy water at all abrasive paper levels.
once you have sanded thoroughly at 1200 paper (with soapy water), wipe dry with clean towel then start polishing with coarse polish 1st and whatever other polishes you have right up to fine bodywork polish,
then you should have crystal clear lenses
you then either need to polish every couple of weeks to keep good or get an aerosol of clear gloss uv laquer and spray them for a better protection.
Good luck

 

I would add that with each step up to a finer grit paper that I would first rinse the headlights off and dry them to make sure that I've removed any residual grit from the coarser paper. And a whole lot easier to polish the headlights with them removed from the car (easy to do on a 996).

 

I ran into a similar issue last Spring. What I found was that the OEM clearcoat on these lenses is incredibly hard. I thought I ruined my lense but a pro (not the Craigslist $40-type guys) was able to save mine and make them look perfect. He ended up having to use 80 grit to get all the clear off. Find a pro and ditch the home kits, they only seem to work if your clearcoat was heavily damaged/corroded.

 

This is EXACTLY (bolding mine) what I am getting the feeling of.

My lenses weren't too bad (car was well maintained), so I'm not sure I should have even gotten into it - but definitely, it would appear that the original UV coat was basically untouched. So removing it seems to be a very, very tough job.

 

Ask around local detailing shops to restore your headlights.

Here's my turbo's before:
FullSizeRender_2_zpsgjr3gvf5.jpg


after:
194D0A9A-9248-400D-8F6E-C52397252266_zpspjav3qwz.jpg

 

I've done a fair number of headlamps with success. Most people don't get the mfg clearcoat off on the first attack at the job, and the clearcoat won't buff. It takes a while, and there's really little benefit in using a power tool until near the end of the job.

Tape off the edge of the body where it meets the lens.
I generally start with 3M 320 wet/dry. Get a decent size bucket with warm soapy water. Not a lot of soap but a few bubbles. Keep the paper very wet, and start sanding. Go all the way to the edge of the light with 320. Once you have the entire lens cloudy with a consistent opacity using 320, then go up to 400 and repeat. Up to 600, and 800 grit and keep working the entire lens with each finer grit using the same wet method.

Once you get to 800, you can change paper to 3M diamond Cloth 1200 then 1800/2000. Some folks find these on a disk, but I do it all by hand. After the whole thing is done with 2000, clean it with clear water. Don't use the bucket water as it still has that milky plastic residue. The lens should be consistent fairly clear from edge to edge. Now you can use the coarse compounding liquid. I generally use Meguir's M105 but there are other vendors. Start with plenty of compound on the lens and use any rotary drill or buffer you want. Just never stop moving the tool around. Don't stop in any spot and use a fair amount of pressure. Keep putting compound on, it'll make a mess everywhere but you need to work this for a while to get into the tiny scratches left behind by the 2000 grit. Rinse again with clear water. Next up is Meguir's M205 Mirror Glaze, and the same process. That should just about do it, unless you want to use the ultra-fine stuff by hand.

Some folks apply a coat of clear after the 1800/2000 grit, but I don't like to do that. The clear will oxidize faster than the actual polycarbonate of the lens and then you have to sand it all back off over again in a year. I just leave the poly lens and touch it up with 1800/2000 grit once a year then polish again.

 

After I refinished mine I added the Xpel film to them. It protects the plastic and adds a UV shield.

I hope I don't ever have to refinish them now because the film is pretty thick and should keep the lights from fading over time. Plus I keep my car garaged both at home and work so the only time it sees sun is while driving.