I mix walnut and corncob together in my vibratory tumbler and use worn out walnut in my dry rotary tumbler, it's what seems to work best for me.
I polish my brass well, it cleans up well in my ultrasonic cleaner, primer pockets and all. I think well polished brass is easier to clean in any kind of tumbler because dirt, carbon, what ever, doesn't seem to be as hard to get off and my primer pockets are clean when they come out of my ultrasonic cleaner and the same would apply for any vibratory cleaner.
It plays hell with trying to find your brass in grass though because it will reflect the grass around it. Duller brass like cleaned with walnut only in a vibratory or rotary tumbler is easier to find in grass. It's just a dull yellow and doesn't really reflect light.