Years ago, (here we go again) Douglas Aircraft Corporation had a surplus sales yard geared to the aircraft assembly industry. Long Beach CA on the North side of the airport. One could buy surplus very very expensive airplane paint very very cheap. We did and hand sprayed painted a very nice, (at the time) 1963 Ford One Ton flatbed duelly.
High school auto shop 2 painting project.
Are there any industrial surplus outlets in the Atlanta area? Big area, might be. Maybe you can find enough surplus high end paint to do your bus. Excellent answers already given. You would not believe the regulations now required to have that legal large bus or truck size paint booth. The permits are extremely expensive. HB of CJ (old coot)
Also....have you considered turning an expense into a fun project and try to hand brush paint your Bus Conversion? Certainly makes things less expensive.....and perhaps more fun also.