I don't think I'd even bother tumbling them. Just shoot.
I ran this same kind of program on about 40 rounds of corroded Pakistani .308 that I have:
Pulled bullets
Measured charges
Re-balanced charges evenly across all the rounds
Reseated bullets
Hand polished corroded spots on the cases
Never again.
They went bang and maybe off a bench you could see a 10% accuracy improvement due to the balanced powder charges, but we are still talking lipstick on a pig here. I've shot a few hundred rounds of the rest over the years with no functional issues, and still have probably 500+ rounds remaining.
Lesson learned: if you want good ammo, load it yourself with good components. If you want cheap blasting ammo, buy it as-is without any intention to "fix" it, because the effort will be a tedious PITA, and the return will be virtually nil.