Low spots after blocking

I think you’re over complicating this. For minor low spots, let your 2k cure out a bit and use your glaze putty. By the time you sand it flat you’ll have so little on there. I personally have never had issues with mapping.

Don’t over complicate your grits either. Everybody does it different. What I do:

Block high build primer with 220. Once it’s to my liking, I spray 1-2 coats of 10% reduced 2k primer to fill in the 220 scratches. Wet sand that 400. Now it’s ready for sealer. For sealer I use epoxy reduced 25%. Since sealer goes on 2-48 hr before paint and any seam sealer goes on after sealer, leave it to your painter to get the sealer on there.