Honestly can't believe this worked so well. SOME NOTES, THOUGH
So I screwed something up with the pour you see here. But actually I'm not entirely sure I did? It looked a bit weird so I inspected it and genius me let the cups fall into the shade and ruined it so I needed to start over again.
When I did, I went just a touch heavier on the glue and also spent more time twirling the bowl around before flipping it over. I got much better coverage, probably because it let the mixture get a little tacky.
However, on the re-pour I decided to try not-at-all with regard to eliminating bubbles and... this was a mistake. You definitely want as few bubbles as possible for best results. Gotta build that vacuum chamber.
Bottom line, this appears to be a pretty decent setup but longevity is TBD. And if you've got some techniques to improve things please share below! But my overall recipe is as follows:

1. Mix equal parts by weight water, acrylic craft paint, and PVA glue. Stir thoroughly but avoid introducing air at all steps.
2. Pour onto inside surface of whatever you're coating. Rotate object for even coverage.
3. Continue rotating for 15 minutes, ensuring every area gets covered multiple times. Mixture should thicken slightly which helps ensure a uniform appearance.
4. Stand object up and let excess drip out, then dry overnight.

Good luck!