Great to see you again! You were one of the people I was referring to and I'm always open to hear your opinions and advice. Thanks!
OK, here's the booth setup. its 12x22. 2 filters on the dividing wall between 2 garages (same size). They are 16x20 and about at eye level (6ft) spaced out evenly along the 22 ft wall. On the outside wall I have a attic fan 7ft up and centered in the 22 ft. I also have a old furnace fan about a foot off the floor and near the garage door.
Now, here is my theory about the dust...
First I completely cleaned any crap out the booth the night before all except for sawhorses and hood and air hose. I thoughly vac'd the floor with a commercial shop vac and new bag. The walls all have brand new paint and new salt treated "baseboard" all around the floor.
On the morning of painting, I lightly wetted the entire floor down and never opened the large outside door. I turned on the fans 1 hour before painting and left the room.
My theory is this: The furnace filters I am using are crap and the fans are sucking dust right through them. #2 I left the booth a couple times quickly thru an interior door.
Next time I'm getting new micro filters, turning 1 fan off and trying to not leave the booth at all.
NOW, which fan would be better to leave run? Up high, or down low? I value your opinion.
PS. lots of related pics on my homepage