I've been making some brass pieces and I was wondering if anybody ever sprayed their pieces to keep them from tarnishing?  I polished them in the tumbler and they're very shiny, I just hate that they tarnish so fast. Has anyone ever sprayed any of your silver, brass or copper? Or is that not done?

I have heard people do that but I am no metalsmith so I do not know if that's not cool to do. 

I tend to use Future floor wax -- got that tip from the seed beaders. 

What do you do, just dip the finished metal piece in it? How long does it take to dry? And how long does it last?

 I've done this with chain (copper) and I know people who've done it with craft wire and sterling. Don't know if you're "supposed" to or not. I've only used the brand Future. Try it yourself with a small piece and wear it to make sure you're not allergic before you put any major pieces into it. I've not found anyone allergic yet, but I tell people to try a small piece first just in case.
 

Take a paper plate and put a little Future on it. Place the piece on the plate; turn the piece over to coat. Hold the piece up and let most of the product drip off. Place on a plastic surface like a trash bag (NOT a paper surface; NOT your table -- you don't wanna know how I know) and let dry, turning once in a while. If it's not dusty or windy, you could hang it up, too (with plastic underneath to catch drips). When it's dry, you may have to "unstiffen" the piece by wiggling it around some.

 There's also a product called Renaissance Wax which may work (pmcsupply has it).