You could try it with a very small pencil. It would be: touching up and immediately whiping off.
When fixing pebble-chips on car hoods (err... zis is a UK forum, so zis is called a bonnet then

), I use toothpicks to just fill and level the the paint layer with a tiny drop (won't work if its down to the metal or already corroding)
Once dry
very fine wet-sanding, polish, etc...
BTW: also I'm still due in shipping my K2 tank and side panes...
Got swamped with other issues and still searching for a really rigid carton... don't want to have that thing all banged up...