Garages work. Sweep and blow out the dust on walls, floor and ceiling a day or so in advance. Then do it again before you paint and let everything settle down. If you need to use bug spray (Raid house and garden) do that before you final wipe the body down. Let the neighbors know so they don't call the cops or fire dept because of the vapor cloud or strong smell of the urethane. It can get ugly in some municipalities if you paint at home in a residential district. If there isn't much wind when you are spraying, set up a box fan outside to help dissipate the exiting fumes. Refer to the Garage painting 101 post on the HAMB for ideas on setting up the fan system and hanging parts. I guessing you have the doors and decklid off. The deck lid is a good place to start spraying and get the mix/reduction dialed in. It's the easiest to do over if you screw up. Blow air into the room and suck a little less out so there is a positive pressure. Keep the air moving well after the last coat, then after an hour or two just a small fan blowing over the body to keep the solvents going away.
Remember:
Tack cloth-used ones are best
Tweezer with needle sharp points
Wipe towels as lint free as possible
Blow gun
Wet or dry sandpaper for nibs in the sealer
Paint strainers
Good mixing container
Mixing stick
Watch or clock
Good lighting
Drain the compressor--the day before and again the day of painting
Moisture separator at least 20 feet from the compressor
Set up a solid, sturdy vertical piece of masking paper to test the spray pattern on.
Do a walk thru (actually pretend you are swinging the gun) the way you are going to spray (ballet) to see if the area is clear for swinging the gun, the layout of the air hose and where you are going to start and end. Try not to run your strokes exactly in the same place for each coat. Vary the starting and stopping point just a foot or so different so you dont get a buildup of material on the same start and stop area. Remember in the spraying video to use the diagonal wetting strokes if you come back over the same area.
Most urethanes are ready for the next coat when the paint film is "finger slick". That means you can ever so lightly run your finger over the paint without it smudging or smearing (about 5 to 15 minutes depending on reduction, temperature, air flow, and coat thickness). Do this test on your spray testing panel (masking paper) or some masking paper on the car.