I went through this with my headlights a few months back.
http://www.stangnet.com/mustang-forums/threads/tinted-my-headlights.855830/
IMO, the Rustoleum lens tint looks better than the VHT, and it sprays a finer and more even mist as well.
Here's the process I used:
1. Clean and lightly wet-sand the lights with 1500 grit sandpaper.
2. Sprayed two VERY light coats of brake light lens tint, Rustoleum brand. And I mean LIGHT, like spraying-a-pan-with-cooking-spray kind of light.
As a side note, I first did this with VHT Niteshades, and did not like it at all. First, the paint came out in large droplets, which doesn't look as good. There is no way to get a 'light' coat of Niteshades on. Plus, it has a bluish-greenish shade to it that is VERY noticeable on a clear lens. The Rustoleum is very close to black/grey, and comes out in a much finer mist.
3. Lightly wet-sanded with 1500 grit after it dried.
4. Two light coats, one medium coat, and one very heavy coat of clear, Dupli-Color brand.
5. After it dried, wet-sanded with 1000 grit to get all the orange peel out.
6. Wet-sanded with 1500 and then 2000 grit to get super-smooth and slick surface.
7. Buffed with Porter Cable + Orange pad with Meguiar's 105.
8. Polished with White pad and Meguiar's 205.
9. Topped it all off with a coat of Meguiar's NXT Tech Wax.
10. Had several beer. With my left hand of course. Because my right arm/hand was about to fall off at this point.
The key to keeping them shiny is the sanding and clear coating. It is a LOT of work; I probably spent 10 hours total on my headlights and corners, but it was well worth it.
Here's a couple of threads I used to guide my way when I did it:
http://legacygt.com/forums/showthre....html?s=20e7f103f214a10c4dc98828d4fc55b3&
http://www.355nation.net/forum/how-exterior/30062-how-apply-vht-night-shades-spray-tint.html