I did the sand and paint on mine. I removed them and did the following.
1) Wash thoroughly.
2) Wet sand with 400gr paper on a 3m sanding block until smooth.
3) Wet sand with 1000gr (couldn't find my 800gr) until smooth
4) Wet sand with 1500gr until smooth
5) Dry assembly in front of Pellet stove (dry however you wish)
6) wipe lens with PrepSol (mild thinner) or alcohol, let dry
7) Spray moderate coat of rustoleum clearcoat ($5 at AZ, wallyworld etc) or equivalent, let flash--10 minutes or so.
8) Spray 2nd coat of clear a little heavier.
9) let dry for an hour in front of pellet stove (warm location is best)
10) Reinstall and enjoy
Sorry, no pics but there are plenty here there and everywhere.