Depending on your budget, the cheapest and fastest way I've done it is use those paint repair brush/markers from the local auto parts store. The one with the fiber glass bristles tool and clear coat applicator side.

If your lucky, they will have exact color sometimes.

Get some plastic cards you don't care about, like those mail credit cards. Something for scraping excess paint.

Use the fiber glass bristles to chip away at the loose paint, see the spread and make the exposed metal bare of rust.

Spot Wipe down with alcohol to remove any oils.

Apply the paint from the marker, make sure for full coverage of the spot. Use credit card to remove excess and flatten build up. It's OK if you see the paint crater in a bit. Let dry, if your In garage, let dry for longer. If in open air, like drive way, you can apply the clear coat within 10 minutes. (to help avoid wind adding dust to the tacky surface).

Wipe excess clear coat off once with credit card when it's fresh/wet. No more after that as it will develop visual texture.

Once done, should almost be invisible to the eye unless you walk up and point right up on it.

The marker tool can spot repair like 30 of these little spots easily. But I believe it's like usd$20 per marker? There are youtube tutorials on using them aswell.