Hi Aaron;
When you have spots where the paint has flaked off, the best procedure is to smooth the edges using a Scotchbrite pad, or the proper sandpaper.
The best type of sandpaper is aluminum oxide sand paper since it’s compatible with aluminum. Using other types can cause corrosion.
After smoothing the edges you should prime the bare metal. After you have applied a thin coat of primer and let it dry per the instructions. Then you can put on the finish coat.
Unfortunately there are many different tints of airplane white.
The original white paint color for your PA 28-140 is called Daytona White. Unless your airplane has been painted since it left the factory.
You can order both a good primer and a good white enamel from Aircraft Spruce and Specialty (www.aircraftspruce.com). https://www.aircraftspruce.com/catalog/cspages/aircraftcoatings.php.
Sandpaper: https://www.aircraftspruce.com/catalog/cspages/sunmightwaterproof.php
However, if your spot is small it’s often more effective and quicker to go to the local hobby store or hardware store and buy a pint of white in this case, enamel paint. If you’re going to hand paint, I recommend going to a hobby or art store to buy a good quality brush. When hand painting a good brush makes a lot of difference.
You should still fair in the edges, and still apply primer first, but if you experiment a little with a brush and get paint that’s very close to the right color, it will look pretty good.
The other option is to take an inspection cover off the bottom of the wing, and take it to an auto paint store for a match. Some stores will mix up a pint. But it will be much more expensive than the small pint of enamel at the hardware store.
Let me know how it comes out.
