I began casting and coating 6 years ago. In that time, and after a few tens of thousands of rounds down range, my PC methods and equipment have evolved. Many of us do similar processes, or at least have some overlap. I've received some great ideas from this site. Tried many and abandoned several.
I'm pretty happy with my current process, after giving about a 2k bullet test drive.
Powder: I am now using powder exclusively from Smoke4320. I find that a blend of two or more gives most consistent coverage, and a little Jet Black added to any makes great results.
Tumbling:
I ran out of BBs a few months ago and found that I don't need them. I use the 1.2 cup round Snapware containers. I have 4-5 on a rotation during a session.
Barely enough powder is added and 45-50 9mm bullets are added. Three of those containers nest nicely in a Cabelas-branded vibratory cleaner (sans media). My method is to have 3 containers "tumbling".
The container that is in the cleaner the longest is removed and bullets are tweezed base down onto a foil-lined tray. 280 bullets per tray.
Add more bullets and powder to the container and swap it out with the container in the cleaner that has been in the longest. Rotate as such until done.
My oven is set to convection at 425. An oven thermometer indicates 400. I set it for 24 minutes (to allow the temp to recover and for the relatively high load). When the last tray is in the oven I size the prior (now cooled batches).
The nice thing about using multiple containers js the ability to use different colors for load identification.
About an hour and forty minutes to coat and size 840 bullets today with very consistent coating results. Start to finish.