I use this:
It is 100% reversible as well. There is NO sanding needed to be done.
This is the procedure that I use:
1. Remove tail light or headlight.
2. Clean thoroughly with rubbing alcohol.
3. Spray the light in stages. I do 2 up and downs.
4. Allow 15 minutes to dry. Then spray until the prefer level of darkness is achieved.
6. Step and love it.
To remove it, all you have to do it spray rubbing alcohol and then it comes off with the wipe of a cloth.