sandpaper

hurc ast

If you're just talking grease and oil, I use mineral spirits in a spray bottle
for the aluminum parts on my motorcycle. There are some aluminum cleaners out
there, but be careful with them. If stray drops get on plastic or rubber, you
may end up with a lot of spotty parts.

if you want to get fairly aggressive a bead blaster using something mild
like glass beads or some synthetic plastic, corn cob, or walnut shell
will work. your local engine rebuilder can probably hook you up for an
hours labor or something else harbor freight has cabinets under 100
bucks. saw one in a kragen ad (you may not have kragen where you are)
for under 40 bucks. just know it takes an air compressor to drive it and
if you get one make sure window covers are available else your vision
will be blurred pretty quick. glas beads arent cheap either but last
quite awhile.
i have a bench top blast cabintet filled with glass beads that works
really well. if you use sand that will actually grain the surface pretty
bad, beads wont.