I have my extremes, and probably shouldn't comment about others. I'm sure you'all are workin it all out.
With my testing, I was looking for tarnish and to solve it. I had run into it just the same after quenching from annealing, so I expected it.
A few days after ultrasonic cleaning I notice a green ring in some primer pockets, and with a borescope I find layer forming and green rings inside cases. This, mostly at corners where water latches hold.
Now I've got a drying problem, right?
High pressure air don't work in corners. Ambient drying is too slow to prevent corrosion. Heating accelerates corrosion.
The easiest, and most practical way to DRY the cases out ended up being corn cob media.
But now my cases are still squeaky clean. The brass surface is fully exposed to the elements. From here, my finger prints cause corrosion if nothing else.. No different than a blued barrel really.
Now I need to cover the brass surface, to protect it, inside & out.
The carbon layer inside of my 'dirty brass' was doing this just fine, and the easiest, and most practical way to COAT the cases ended up being corn cob media -with a bit of polish.
Now I need to do something about bullet seating. I don't want to gall or cold weld bullet jackets, and I need the consistency in seating forces i've always had with a carbon layer.
Yeah, I could go to using moly or graphite,, or I could leave the carbon in my necks alone.
Now I wonder about 'carbon build-up'. Just what kind of a problem is it really?
I pick & scratch around inside a bunch of cases, once in a while pulling a small flake, and with 50 well used 6br cases I couldn't assemble a gram of loose carbon. Seems to me the sizing cycle in firing would dislodge most, shatter it, & what happens from there matters about as much as that laying loose in the bottom of my bore. Maybe it would build up to more of an issue with magnum cartridges and/or surplus powders.
I pick a lot more carbon from primer pockets. But this is not the same as carbon inside cases. Primer discharge, by design, is extremely dirty, and what remains in the pockets didn't get crushed, burn up, and blown mostly down the bore. It affects primer crush on seating.
But a swipe with a pocket uniformer takes care of that issue.
Then I toss it into corn cob media, with a bit of polish, and all is well taken care of.
Well, not quite. Don't ever leave brass in corn cob media, with a bit of polish in it, -for a few days..
Clean the brass, & directly separate it from the media.
This will look good enough, load & shoot fine, and won't tarnish in the near term.
I'm sure shiny brass brings in the ladies (to check their makeup), but I can't come up with any gain in it.