Bill,Sounds kind of odd but dry tumbling with rice and baking soda added works very good and as far as I can tell does not remove the carbon from inside the necks. It cleans the brass much better than the corn cob or walnut media or anything I've tried in the past with no clouds of dust from the tumbler at all.
EDIT: I do run a brush in and out (1 pass) of the necks once removed from the tumbler.
The pins remove all traces of carbon in my casesTumbling doesn't remove inside neck carbon. It will remove some outside neck carbon depending on how long you leave it running. I use corn cob media.
Slight?Slight tangent;