I just got my vibratory tumbler with Walnut and Corncob media.

I have metal rods, about RC 60 that have tooling marks (from the lathe) that I want to remove. I am currently having them sanded by a guy here, but there must be a better way.

I have a couple of rods going in the Walnut now for about 8 hours so far, giving the rods a little more shine, but not smoothing over the scratches.

What would be a more aggressive media that could remove actual scratches before going to the Walnut?

BTW, I don't mind running the tumbler for extended periods.

Thanks, guys!