When primering a little dirt won't hurt as it can be sanded out. It is during topcoat application that dirt becomes a real problem. Plastic and lots of lighting are your friends:
Manufacturer's paint specs hung for quick reference (for both basecoat and clear coat):
A sheet of masking paper was taped to the plastic to use for pattern testing the spray gun.
Although I hate the looks of them, flystrips were a lifesaver as the garage was full of them the day before. Not a single fly found there way into the end product:
Other side of entrance door that connected to another room was used as an exit:
Fans are in a outside doorway and are covered both inside and outside with filters. Air is being blown out:
The OP's big fan would have been a better choice but none where available at our local supplier the day before I wanted to paint. Without a professional type filtering system, I am not sold on blowing outside air into the paint booth.
A simple wooden frame was built out of inexpensive 2x4's to hold the plastic, fans, and filters. Duct tape is used for sealing.
Air inlet:
Additional fans were put here (pointing out) to remove the remaining spray that was in the air just after the final coat. Again, a 2x4 frame was used.
Contractors bags make great wheelcovers PLUS once you are done you can use them to gather up all the dis-guarded masking.
Oh, the final product once assembled: