James - Some of this depends on the quality of your castings but it
looks like you are working too hard. The hand polishing stuff is
getting in the way of a decent polish.
Remove investment, trim and grind sprues.
Run in steel shot, 30 to 45 minutes, no more. This hardens the
surface so that the abrasives will only cut the high parts.
If, and only if, your castings have very detailed surfaces and
you want the deep parts shiny, run again in pin finisher.
If your castings are somewhat rough, run in medium abrasive media
in a vibratory tumbler, flow-thru process for 6 hours.
Run in fine abrasive media, flow-thru vibratory tumbler for 4
Run in steel shot, rotary tumbler 30 minutes.
For high polish, run in dry media, vibratory tumbler, charged
with Simichrome or Chrome oxide, for 24 to 36 hours.
Bottom line - Do not, ever, hand polish something that has been
tumble polished. You are digging in through surfaces prepared for
long lasting effects. The liquids that you use in the wet processes
take off the surface scale.
Your time to run this sequence will depend on the size of your
pieces - if large, you can easily screen the media from the work
pieces. If they are small, string them in some way to make separation
Now you can breathe and let the machines do their thing. No overtime