I work for a body shop. Technically it has to be repainted. But what I do for touch uses are
Wet sand with 3m 28 grit sand paper on a hard block.
Apply paint. Allow time for each application to dry and do so in thin coats.
Once Paint is above Paint lightly wet sand even with paint. Again with 2kgrit.
Apply a light dab of clear. Allow to dry for about 8 hours. Typically over night.
Then wet sand with block 1k by 3m. Then step up with 2k and 3k trizact.
You can even 5ktrizact if available.
Then use rotary buffer to buff and polish back to a shine.
Hope that helps