I'm with bds, the walnut works better for cleaning, then corn cob gives the polish, as a matter of fact I have 2 different containers and I don't mix the two.
I deprime the brass with a universal depriming die, the tumble with wallnut and a used dryer sheet to keep down the dust, when "clean" I put the batch in the corn cob media with a polish (Frankford Arsenal), to bing it to a "like new"shine.
Make sure to keep the dust down with used dryer sheets and wear a particulate mask when servicing the media!