aluminum trailer cleaner works good on a lot of it, but some of the small nooks and crannies require plain old elbow grease.... I've done a few, usually I start with some 80 grit on a DA to get rid of the casting flesh, then progressively finer, all the way to 2000 grit wet sanding, then get out the mothers and go to work. Sisal wheels and jewelers rouge (or however the heck you spell it) works a bit better then mothers.