Here is a guide I did a little while ago about tinting the rear lights. Cost under £10 to complete!
It is quite an easy mod to do but it takes time to mask up the lights.
I keyed ( lightly scratched using fine wire wool ) the entire lights before doing anything.
I used coachline first to mask the outer circles on the lights and then standard masking tape to the edge of the coachline:
I sprayed two layers of e-tech with the lights in a line so I could get an even coat accross them and used a heat gun to dry them off ( the bodyshop should have closed 5 hours before and I was still in there!
)
I then removed the tape and sprayed the lot with 3 coats of clear lacquer and viola you have the finished item:
Hope this helps