That sounds a lot like how I apply it, thanks for the post! I use a single across-grain stroke to get the varnish off the brush, and then X strokes to spread it out. Finally, tip it off with the grain.

It's got to be a dust problem. I do notice that the re-coat is a little better than the initial bare epoxy coat. Actually, it's like the particles are more uniform and evenly distributed. I sanded to 150, I'll go to 220 now. Maybe that will help. Also, it sounds like a spring cleaning is in order. After I put the air filter in, I went around on the scaffold and vacuumed dust off of all the surfaces above; the heater, the trusses, lights, etc... A good blow with the leaf blower might go further.

When you sand between coats, are there shiny spots (lows) left in the prior coat? Or do you take it down uniformly dull?

I tried to talk the wife into letting me make the guest wing into a clean room, but no...

I like the Pettit varnish, it is a little thinner out of the can and flows nicely.