I have been noodling on the paint question for a while and despite recent attempts, I'm still a long way from a solution. I was considering creating a booth out of plastic tubing (or alum tubing?) with sail cloth forming the walls. I'm sure there are all sort of challenges to overcome but i saw something similar for a car paint booth on YT that sparked the idea. I wouldn't glue the tubes into the joints so it could all come apart and pack up tightly when not in use. If i remember correctly, there was zipper for a door like a camping tent. it was an interesting idea but the whole painting thing is a big rabbit hole that i'm not prepared to enter at this time. I'll watch how you approach it Andy!