Or the orange-ish brown fingers.
Are you using your fingers to dig the brass out of the tumbler? Is that the Lyman tuff-nut media? Red rouge treated? That's some crappy stuff, most do not stick with it very long, leaves a fine film/like/dust on the brass.
I did not say I use ground walnut shells. That is fine corn cob media. I also use a media separator made by Frankfort arsenal.
A couple-3-or-4 spins of this separator get ALL the media out of the cases. I have a case feeder on my dillon 650. If there was media left in the cases, I'd know about it real quick. There's a hole in the back just for letting media get out of the bowl, there's none coming out of there.
Getting cases any cleaner than this is not needed.