I have in the past used a brass polisher with walnut media from the local gunshop. Does a good job just dont overload it. havent seen 1 in a while unless I go to a gun show. plug it in check in morning still dirty, check after work... most of what I have done was ready in 4-5 hours
Brad

http://s320.photobucket.com/albums/nn343/brsdb3381/Tuesday_MY_56_Chevy/

56 3100 6 cyl