I agree on this except for most of us (me included) a professional paint booth is out of price range, use a strong fan and keep the fumes out, a little common since goes a long way. I have done several paint jobs and if your air is really filled with atomized paint your paint job is going to reflect that and you won't get a good slick lay down of your paint also. Size the exhaust fan to the room and crap can the old box fans.
Something to think about, I worked on residential job sites for 26 years, here in MO a painting contractor is hired to spray and finish the wood trim and doors and on new homes the cabinets, 99 percent of this time its done with lacquer (about the most flammable of all finishes) out of the hundreds of houses I personally had been in 1 used a mask, and nearly none where evacuated of fumes. Was it dangerous you bet, is it done? yes daily by countless professionals, a friends cousin was killed by doing this and hitting a drop light which ignited the whole mess. We had a paint booth at work (homemade) and the epa and other agencies are on shops to make sure all this is done according to osha and safely but the majority of violations are done on unpoliced job sites, by the thousands daily, no booth or anything, like I said common since (and insurance) here goes along way...really, if you know how a engine works we all know the risks.