I hit on the idea of using a kitchen sieve to wash the excess rouge out of a tumblerfull of the treated tufnut media. Worked pretty good, a lot of red stuff ran down the drain. The media is still red, but it doesn't rub off on my hands. I spread it out on a couple newspapers on the kitchen counter to dry, which didn't take too long as it didn't really absorb any water. The problem with the tumbler itself was that the edge of the drum as well as the driver rollers got glazed over time, so with a heavy load the drum didn't want to turn- it just spun it's wheels so to speak, which just made the glazing worse. I took a small disc sander and roughed up the surfaces & it works real well (for now anyway).
I've got a small batch of 38 cases tumbling now, guess I'll see in a little while how well the de-rouged media works.