Hadn't thought about the motor-driven bomb issue. I read something a while ago dealing with making up a paint booth using visquine (clear sheeting) hung from sched 40 PVC sprinkler pipe and clamped together with spring clamps to prevent damaging the sheeting. Duct tape should work as well.

Use of the filters was required, but I think they said to put them between the box fans and the booth, and force air into the booth. I think that avoided the vapors/sparks issue, if memory serves. You'd want something to either filter the exit air (to prevent backflow) or to seal up when the fans stopped. You're applying positive pressure by blowing into the booth, so you can even open up a "door" to walk out after painting.

Reminds me of our old boss at the JC where I worked 30-odd years ago. He painted the college vehicles in the mechanics' shop one week, and had a sign on the door that said "Open this door if you want to die!" He had us hose down the floor, but we couldn't hose down the pit, or the walls (electrical) or the ceiling (too high). Paint wasn't bad.... at 50 feet.

Oh, the visquine booth also seals the vapors away from the lights and so on, if you vent it outside through the garage door like you were discussing.

I'd think about an old swamp cooler, fitted out with filters, as a fan to blow into the booth. Good discussion - I need to paint a couple of cars this summer. I'm planning on using the visquine booth, but will watch for other suggestions.