1. Go to your local auto store...
2. Get a can of the spray on decal remover.
3. Apply a heavy coat to the painted lights, and then wipe off after 5-10 seconds with a rag or cloth. Then rinse.
4. Repeat if necessary.
5. ???
6. Profit.
I figured this out today after paint thinner was taking forever... Also this didn't fog the plastic like paint thinner did.

Good thing about this stuff is it wont harm your paint if you don't feel like taking out your tail lights. I would recommend washing the car right away afterwards to get off the decal remover that might have ran into a crevice. It can't be too good for the paint to let sit on there though..