Repairing Drip Rail (above the door) Paint

[Naby]

The drivers side drip rail once had an antenna clipped to it and so has some light surface rust. Also, there is a slight crack in the paint running down the entire length of the inside of the drip rail on both sides. What is the best way to repair and preserve the paint in this area? I know the rails can be major rust problems on these older trucks. Where can I get the touch up paint for the repair that matches the factory paint?