[trumpetdropper]

I struggled to make a difference with the generic lens restoration kit I bought as the yellowing was very thick.
I also tried a DA polisher with some rubbing compound which would have worked if I had had the patience.
Instead I got a brilliant result using very fine wet & dry (1500 git & 3000 git) it cuts right through the factory applied coating easily but use plenty of soapy water. You do need a fair bit of elbow grease, but it's worth it.
I then did a DA polish with some glass cleaner and final bodywork polish and they came up like new.
Taking the light units out of the car and done on a bench is better too (especially for you back!)
I recommend that before you drive around/use your nice shiny lights that you protect the lens surface with a hard compound chemical (nano) paintwork sealer (9H nano sealer - small bottle cheap on eBay) otherwise the sun and salt and general road dust will soon have the lenses deteriorating again.

Andy