Painting bullet tips

[Pit4Brains]

Sharpies all the way..
Very helpful when you fumble a box of rounds with varying powder charges..
I do the bullet tips since they face up in my box.

 

[VenomBallistics]

stazon ink from the stamping section of most hobby stores is probably the ideal thing for you.
I would not worry about paint contacting the bore, You'll just burn it off with the next shot anyhow