Detail gun with the right air cap (mm hole) for the paint you are spraying. Depending on the color coat vs the primer, you may have to compromise here.

Look at the CFM @ psi your gun/cap requires, and buy a compressor that meets those requirements. You won't be using a 100% duty cycle, but once you start spraying, it's fairly continuous. Be prepared to pay up for the compressor.

And like sloar indicated, the right weather. I get about 4 weekends a year here with the right temp with low enough humidity. YMMV. If you can paint inside in a controlled environment then you're golden. I can't.

I use an air dryer between my compressor and gun.