Once you get down to a 400 grit wet sand you can start rubbing it down with automotive rubbing compound . A bodyshop or auto supply store can set you up with that . Then finally a polishing compound will bring out a refective smooth finish almost a chrome look . You can get that at a auto store too . You should be able to get small cans of both at Walmart in the auto section .P.S. you will need plenty of soft rags as they will get a black residue from the aluminium .