"> I.e. can you use general "acrylic" paint made for home reno's and the like
Not sure what you mean by Home Reno's. Although I'm assuming you mean something bought at Home Depot to paint a ceiling.
All paints are not the same - in particular you have to worry about thing like fineness of the final layer which is not always the same. Putting ceiling paint on a model would most likely not cover or set properly if thinned too much or obscure detail if used out of the can. Acrylics may be somewhat different than solvent based paints - in these there are pigment "Grains" in a binder and solvent. The Solvent evaporeates and the binder fully sets (some times takes a week) and holds the pigment in place. Pigment size in the hobby paints is much smaller, and thus the final layer thinner
Many years ago a friend build a model of the Mohawk aircraft. He got actually aircraft paint at work (Grumman built the aircraft). It looked lke the aircraft was painted with a mop or a trowel - total disaster.
I can't help but wonder if you're going through so much paint if you don't have too wide a spread on the nozzle of your airbrush and are wasteing a lot into the air. What type of airbrush do you have, and which nozzle are you using.