I've used this on a number of cars with good results.  But that comes with a caveat - I've painted a number of cars, and this will not hide any imperfections.  Your tailights needs to be clean and shiny beforehand.  I've had the best luck by getting a3M Headlight Lens Restoration Systemand polishing the taillights first (follow the directions; basically you just skip the regular paper and do only the foam-backed 3000 grit followed by the polish).  Once they're smooth and shiny, get yourself some paint prep stuff (I like theseDupli-Color Grease and Wax Remover Prep Wipes, but you might be able to get them cheaper in a store).  90% of a paint job is prep, so make sure you prep very well; if you use the wipes, wipe in one direction, and then wait until the lights air dry.  Once you've prepped, your skin does NOT touch the surface again.  Wear some disposable nitrile gloves if you can't control yourself. :)Spray on 2-3 fairly light, even coats.  You don't want to put more than that on, or the lights will be hard to see during the day, and someone will crash into the back of you, ruining your pretty tail lights. ;)  Once you've gotten the lights darkened, spray on a few coats of the clear coat.  Try not to get it on heavy enough to run, and try to make sure it's going on wet (no dry overspray).  I like to put on about 4 coats, and then after it's all on, go over it with the tail light polishing kit again (start with the foam-backed wet sand paper, then follow with a rubbing compound and finally a scratch remover by hand; I like using the Meguiar'sUltimate CompoundandUltimate Polish) to really polish the clear out.You don't have to clear over the top of the niteshades, but since it's a translucent coating, you can't sand or polish it directly without screwing up the color.  And it tends to fade over a few years if it's not protected from the UV rays with a clear coat.  Or at least the older version did; they've changed the formula a little in the last decade or so, and maybe the new stuff's better.  I still clear over it, though. :)