Cheap HVLP unit ended up working just fine - 22"x30" on primed canvas (color is from tinting with oils). I made a darkroom spray booth and enclosed it with construction plastic, 2 exhaust fans and a respirator. When I go larger, I'll come up with more of a full-face, forced-air respirator setup. But very pleased, it was pretty quick and easy - three coats, no thinning or Photo FLo added. After coloring the canvas, I varnished it - looks about a foot deep!
Yes, sort of "twisted Pandora". The model has become a family friend after a couple shoots and stays with us when she's in town, we got a head's up that she was booked near us so the Mrs. and I made up the spare room and I went on a prop hunt, saw the box and said "aha". Shot her 4x5 on white seamless, then built the wall model and composited with a masking kit, no scanners or pixels. Took a year on and off, but lots of "infrastructure" I'll be using for a while.