my experience with tail light tinting (minimum) the vht nightshades stuff is pretty good but remember it is paint and you have to treat it as such. but what i did was did like 5 coats until i built up enough i couldnt see very much then polished the crap out of them with a 7000 grit buffing pad until my desired tint. then clear coated it and polished again. looked amazing and completely matched my black car and the polishing method makes it look like glass while taking minimal amounts of shade off. if you have any questions tho i can give a full runthrough.