Walnut is more aggressive that corn cob.
Both can be dusty when they are dry.
Corn cob is fairly absorbent, it can soak up a fair bit of liquid (oil, moisture, or solvent) or grunge.
I find that corncob, with a couple of tablespoons of Varsol, to be quite effective (it shouldn't be anywhere near visibly damp or clumping). Not only does it control the dust of the corncob itself, but it will also dissolve case lube and then wick it into the corncob, and it also wets and clumps any other dusts too.
If you are at an industrial abrasives place, choose a grade that is fine enough to not get stuck in flash holes; the corncob that I bought years ago seems almost perfectly sized to lodge a single piece in most of the flash holes. It's easy enough to poke out, but it would be nice if this didn't happen so much.