With a small compressor you'll want to go slow. It's hard to get an even coat when your pressure is constantly climbing and falling. As pressure changes so does the output from the gun. I've done rustoleum jobs with portables before, uneven finish doesn't matter cause you just throw a couple more on top of it. I likely wouldn't do a 'good' paint job using one since good paint costs more than $20/gallon
But it's been so long since I've done a good paint job I'd probably prep and then hand it to the pro's anyway.
Actually I'm getting older and my bank account healthier, I'd probably just give them the keys and tell them to call when it's done.
But I'll rusto my offroad projects any day of the week
Back when I did my first car you ended up doing a ton of primer work, by the end of that you would have a pretty good hands on education as far as running the gun/pressures etc. And if you f'd it up, just sand it down and start over again. Primer was cheap.
And sanding OMG the sanding. I still wake up at nights haunted by the sound of a distant DA sander.
And then WET sanding, and then COLOR SANDING NOOOOOOOO! hehehehe. But I did have a purple mustang with a finish so fine you could read the smallest print in the reflection. Just a giant purple mirror after spending about 6 hours per panel color sanding and buffing when it was done. It was a long project., 3 hours a day, 5 days a week minimum for a year on just the body.
Then a few years later I traded the mustang in, 2 months later the nimrod that bought it wrapped it around a tree.