If you just want some grip back on the caps and to take the physical shine away, 2000 or 1000 grit wet or dry sandpaper will do the trick cheap and easy. If you do have to use sandblasting, just do something soft and fine grained. Loading up some plain old baking soda at 90psi is alright for the job. Sandpaper will give you the most control over a curved flat surface. Media blasting will dig at the edges and sides too.
If the shine itself doesn't bother you, but the unequal shine does, then just polish the whole lot with a paper towel and any good polishing compound. Plain old toothpaste will work in a pinch.