Steve,
I painted in my 2-car garage with the doors open. In the rear of the garage, I cut a hole in the soffit and added an old house A/C/Heater squirrel cage blower inside, blowing out. I did not water the floor but I did use a leaf blower a few days in advance to blow out most of the dust from sanding. Houston has a different temperature problem than Seattle. I painted early each morning when it was coolest.
Since I painted the car in pieces, I had the option to hang things or lay them flat. Each has different disadvantages. Flat allows the paint to lay thicker without running, but it was harder for the paint in my gun to flow when held at that angle (gravity fed HLVP) -and you've really got to watch that air hose. Primers are easier and more forgiving. Color is easy to see. The clear coat was the hardest to see and easiest to run. -And it gets everywhere and everything in the garage will be sticky. Even the bottom of your shoes. A little dust in primer should not be a problem. What is irritating is a butterfly with one wing stuck in fresh clear-coat and the other trying to free it. I found a black cat hair in my hood after the second coat of clear. After all the other coats of clear, and all the ultra-fine-color sanding, I can still find that cat hair. Our black cat is 13 years old, and I hope I have his hair as a reminder for a very long time. -I tried to show it to my wife, but otherwise no person has ever seen that hair.
Take your time. You don't have to do your best -good enough is probably good enough. You have arrived at the fun part.
Get a good respirator and use it -I couldn't even smell the paint until I took mine off.
Jer