Sand the headlights with 1200 grit sandpaper [wet], be sure to rough them up pretty good to get proper adhesion. Spray the headlight with Bullydog adhesion promoter [clear], then Mix very little black paint with clearcoat & spray 3 coats. Be sure to get clear to flow around the edges of the headlight, rough edges will cause it to flake off.
we used tinting on my friends one layer on the inside and one on the out seems to work, im not sure what % it was but it looks pretty good and really cheap
i have used the VHT Niteshade spray on tint on all of the lights on my truck except the headlights and it's turned out perfect. This is the cheaper alternative obviously to buying new headlights but it works for me and is cheap, easy, and looks good.