I blasted the back of my iPod and it's great. I never wipe it down because scratches and fingerprints just don't show.
However, for plastic, you're gonna have to use fairly coarse grit and it's gonna be real tough to get an even finish. I think the IceBook's outside is polycarb which is very resilient. We have some coarse black grit that looks like crushed obsidian, very sharp granules. Something like that ought to work. Get some Lexan scraps to practice on. I used it(on the inside as light diffuser) on a Pro-keyboard I backlit, and the finish was a light frost, but was very hard to keep it uniform.