Don't shotblast the aluminium wheels! the pits it would leave would look more like a lunar landscape, than wheels! glass-bead blasting is what you need to do. (often confused with sandblasting/shotblasting) Medium of 00 or 000 grade would be ideal. the beads shatter, rather than pit the metal. Best sources will be metal finishing shops, and precision machine shops. (a local pistolsmith has done alot of bead blasting for me. they bead blast steel, before blueing, to get a matte finish... but it does look funny, to find a set of valve covers in a gun shop.)