Got a bit better polish on these! I've been a little more ruthless about kicking out stones with rough spots after step 3, washing between steps with some (very ancient) white king soap flakes, and checking the polish progress every few days. I pulled the brightest and put the rest back in for another day and that seemed to help. The brightest five stones had some minor flaws and I was wondering if the rough spots were causing problems with the rest. Either way, got most of them to to take a nice shine! The ones that didn't take a polish are still attractive for pond rocks and will gravitate into the backyard fountain at some point. They're in the small dish. All are Washington beach agate, quartzites and other oddities. This is my first time using the Tripoli polishing compound and compared to Cerium I think it does leave the rock a little brighter. I like it.
I have another set fresh from its wash cycle and in polish now. The most recent batch of step 3 grit I got was 400, versus the 600 I was using before, and it does seem to leave the rocks with a much more matte finish than I'm used to. I keep thinking 'these aren't possibly ready for polish. what am I doing wrong.' Last picture is of the post-step-3 rock that's now in for polish.