I use a vibratory tumbler with a heavy dose of Flitz media polish added to it. Brass cases cleaned for eight hours or more come out requiring sunglasses - much shinier and smoother than even new brass.
I will however caution you with regard to older bottleneck rifle brass. I have three 20-round boxes of Remington 6mm REM cases that are once-fired factory loads from the 1970s or 1980s - they are in the old green Remington boxes. I also have some 100-round boxes of new late-production Remington 6mm REM cases and was recently going to use one of those older cases to replace one of the newer ones that was lost.
Just for grins, I decided to weigh the two cases to see if there could be any pressure problems with doing that and found the older cases weigh ten grains more than the newer ones. Could their thicker walls cause enough of an increase in pressure to be a concern? I didn't know but have relegated that old brass to my "collector-item" carton. You might want to check your older .30-30 WIN cases too.