recommendations for auto touch up paint

[NIck Miller]

Yea, differentiation between a base coat primer and a rubberized
undercoating for the bellow decks of the car...

I'd Call your local NAPA.  They carry a ginormous book of paint codes and
have the ability to mix together a can to match your factory color,
including the mica/metalic flakes.  usually works pretty well.   You can
maybe get the roller-pen for like a deep scractch, but if you're talking an
area greater than 1x1 you'll need to go the full 9 yds and sand it, prep it,
prime it and paint, and try your best to blend it well.  I'm certain if you
search on google or youtube you'll find a nice writeup of how to go about
this.  we just did a few spots on my mothers buick near the fenderwells.