I have used luster dust several times to try and achieve a metallic look with silver or gold. (think chrome on a car cake) and it never comes out right. It's too opaque or streaky. I have tried it dry and with a little vodka and it never works. Am I using the wrong product to achieve a strong, metallic finish.

I'd love to know too! Just yesterday I saw this cake by SHogg where she said she painted the letters with super gold. http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1245284

You are using too much liquid. Let it sit a couple of minutes (1-3) until it is a bit more on the thick mud side. You have to work (painting) rather quickly, but if it starts to glob on you just add another drop of vodka. You can keep doing that until you are finished. Any silver left in the dish can just be left to dry, then when you want silver again, just add a few drops of vodka and go for it