Facility....is the most important tool for painting. Trying to paint a car, bike or anything in a garage, shop or outside in the back yard, is not going to work out well. Way too many problems to contend with. Been doing it for years, biggest problem with a shop or garage is ventilation, and not for ventilation for breathing. If you do not have a booth, with proper air movement, or a garage with minimal exhaust, and say you are using acrylic urethane, to replicate a enamel paint look. By the time you have applied your 2nd coat, and ready to apply your finish shine coat, you would be amazed at the loss of visibility due to airborne product. Product in the air will hamper the light in the work area as well. So even before anyone begins to even think, that it is an easy task, with out the proper tools, it may end up as a educational moment...
Gave in, and installed a Devilbiss drive thru booth in my shop, ten years ago.
One more point.... The best paint job is on the best prep job... Prep is everything!!!