1. What kind of plastic are the foglight covers?

2. Best way to get what appears to be the rattle can paint off?

In researching how to get the paint off the plastic foglight grills I have found the following:
1. vegetable oil
2. nail polish remover
3. oven cleaner
4. DOT 3 brake fluid
5. Testors Easy Lift-Off
6. Castrol Superclean
7. Simple Green
8. isopropyl alcohol
9. Purple Power
10. Windex ( for acrylic paint)
11. Tamiya Lacquer thinner or Gunze Mr. Color Thinner
12. bumper stripper
13. blast with baking soda
14. WD-40

Buy new ones and relive yourself of a lot of wasted time and elbow grease.

I would lightly sand them then prime and paint.

Sand with 3m pad and some fine drylube sandpaper,clean with paint prep degreaser and topcoat with what ever colour you like,hard things to paint but do it slowly a bit @ a time over a reasonable period of time.
If you think it might not stick buy a plastic primer ok.
Good luck

Plastic is old and it's seen plenty of contaminates. Buy new ones.

My recent experience with soda blasting says if that works really well. I bought an L cheapo $20 handheld blaster from Harbor freight and went through about 20 boxes of baking soda on a small project and it worked like a charm. It also leaves and I surface I want you wipe down is good for painting.