This time I hung sheets around the workpiece, closed the windows, turned off the air, misted down everything every 30 minutes with a spray bottle full of water, used a tack cloth continuously during sanding instead of letting it build up, and dipped my brush in mineral spirits to displace air bubbles before first brushing. Five hours later...

Still bubbles everywhere. Goddammit.

I know it's not dust because I can break them with a well-placed drop of mineral spirits.