My policy with this kind of thing is: Don't worry about what it looks like. Just get that metal protected so the rust doesn't end up eating right through the panel!! And don't break the bank doing it - because it's just not worth it. You take it to a body shop and they're gonna try to whack you for $500 or more, then next week it'll be another spot somewhere else.
So I would just start by meticulously sanding it down (using various increasingly fine-grit sandpaper ... maybe 150, then to 300 or more). If the metal is pitted, you'll need to apply a thin film of that red body putty, then sand that down. Once that's smooth as glass to the point where you can't feel any uneveness, wipe off the dust, mask it off, then prime it with a quality primer paint.
Do several *very light* coats (instead of fewer heavier coats), allowing each coat to dry adequately. And keep the spray nozzle moving continuously (moving it before initially pulling the trigger) ... so you don't have any runs or drips. If you DO get runs or drips, you'll have to sand those out (super fine grit) and repaint (just more time). It's a good idea to make some practice coats on a scrap surface to get a feel for the timing and technique of your paint stroke.
Then finish it off with a top coat paint bought with the vehicle's paint code number. Again - do several "very light" coats of paint.
Then, lastly, spray on your clear coat.
And don't spend more than $100 on materials. Clean up and store your leftovers for the next touch-up.
2011 Equinox 1LT (new Jan 2011): Summit White / 3.0 L V6 / FWD / Pioneer Stereo / 18" Wheels / 131.6k miles [14-JUN-2019]
2002 Impala 1LT (new Jun 2002): Summit White / 3.4 L V6 / FWD / Cassette-CD Combo /222.5k miles [13-JUN-2019]