Your media is still good, the brass is tarnished. Throw out the brass.
NRA Life Member, Air Force 1970 - 74, S&WCA # 2533 Inactive, S&WHF #366
2019 New Years Resolution: No more gun purchases
The 20 pound bags of reptile bedding (intended for snakes, lizards and other reptiles) is coarse ground walnut shells, exactly the same thing sold by gun shops as walnut polishing media. The difference is the quantity and lower price. I've had a bag for years, and it's only been tapped a few times.
The dryer sheets will gather up dust from the media so that you can throw it away after a cleaning. This extends the life of walnut media.
The magic comes with the words you say when turning on the tumbler's switch. They're secret words, and you have to know the sign before I'll speak them. (Hint - think bright and shiny).
Ok... twist my arm: "clara et crus".....
Before I tumble brass, I separate, inspect and wash it with dish detergent in the sink. After thorough rinsing, I dry it. Only then do I put it into the tumbler with a little polish. Make sure the polish doesn't have ammonia in it. That chemical reduces brass.
I clean several thousand range brass pickups this way, and have good results.
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accipere facile, sed sumite! - Take it easy, but take it!
NRA Certified Instructor: Pistol; Personal Protection Inside and Outside the Home; Rifle; Reloading: Chief RSO
NC DOJ Concealed Carry Instructor; Appointed Member North Carolina Criminal Justice Information Network