First off, wrong time of year, you need 70F or above and if you bring in fresh air from outside it won't be anywhere near that so you are going to need one heck of blower heater. Couple six pairs of hot lights would not hurt either to heat up the spray surface. Try to get the concrete floor as warm as possible so that it will radiate heat.
You will also need some panel filters like you use in hot air home central systems to prefilter the air. You should spray the floor down with a light misting of water to keep dust down. Couple of window fans, both on exhaust, pull the clean air in thru the filters. Tape/seal all the other cracks including the cracks on the panels on the garage doors.
Also one good paint quality respirator rated for the paint you will be shooting. Now a days with whats in the new paints and the booths that are required to shoot them I'd look at some kind of moon suit or pressurized head piece for the extreme end, a dual filter full face respirator at the cutting it close end..
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Yea, I know, I'm cautious but then I've been around a while and seen some of the people I knew that did not think about it, heck I was one, working part time at the local gas station, up to my elbows in gasoline and solvents for hours never even thinking about what I was absorbing from those crudded up motors let alone breathing... and if you think I'm kidding read the warning labels on Dupont Imron or the camo paint the military uses, deadly stuff.
Also the garage, are there bedrooms over it ? People living up there, the fumes, volitiles and outgassing will for sure seep thru the floor above..
Have you considered having your local vo tech do the shooting, lot of them will do it for free or just for the materials.