Question for the experts. What's the best method for touching up small nicks in my paint? Should I use a fine artists brush, Q-tip, etc.?

A toothpick works great. You only want to deposit the paint in the nick, not around it. Build it up slightly higher than the surface, wet sand with 2000 grit on a sanding block and buff.

Old bodyman's trick is to use the torn off end of a single match.

Hold the redhead between your fingers and dip the torn off end in the paint and just barely dab it in the chip, not around it as stated before.

That part about holding the "redhead" is up to you LOL