A friend and I installed 3M glossy vinyl wrap on my spoiler the other day. It costs about $30 for the wrap (1x5ft) and comb (to smooth the surface). You'll also neat a heat gun (or blow dryer) to stretch the vinyl to fit properly. It turned out pretty good. Didn't look too good on the bottom... but who cares! Spoilers on GEN II prii tend to fade after a few years. Here's a quick look: Before: After:
Nice job, I have previously painted the roof with black marine paint on my silver Gen2 Prius after removing the two silicon rubber roof drain channels. I might have a go at vinyl wrapping the spoiler.
We'll see how the vinyl holds up over time. I'm a teacher... So I don't have a lot of $ to throw around for stuff on my car. Btw.... This touring Prius is great!