Very late response here,
But if you have a cheezy Sears sandblast kit, you can use baking soda as a medium. I've used this stuff when "sand" blasting carburetors. It's very gentle, but will clean aluminum very nicely.
I stick the suction tube right in a big bag of baking soda (big bag of baking soda purchased cheaply from Costco, BJ's, whatever). Of course do a test on something first!
I bought my sandblast kit from sears for 50 bucks some years ago, maybe harbor freight has them now?
Good luck!