Some hobby shops carry it, but I bought mine from eToys (cheapest price). I bought a spray can, although it comes in a bottle too. Only need one can for both lower trim panels.
I removed the dash pieces, which was pretty easy. Hardest part was picking a day when I didn't need my car (had to wait for the paint to dry before reinstalling the trim).
Coolest part about the paint is that you polish it after it dries. The more you polish it, the more it looks like metal. You can basically make it look like anything from an A4-style dull aluminum to a highly polished aluminum.
Don't forget to buy a can of clear to put over it after it's all done. Thanks for the thumbs-up!