yetiwagon

A couple of weeks ago, I was getting my friend's dog out of the car. She saw a squirrel and lunged, and because because I was still holding the keys, they got caught between the door and the jamb. I ended up chipping the very edge of the driver side rear door and the corresponding spot on the next panel. It's small (about the size of a pinky toenail), but it's down to what appears to be the primer (silverish).

I have a touch-up kit from PaintScratch but I'm not sure the best way to go about it because of where the chip is. What kind of brush/applicator would be good for this type of job? And do I need to leave the door open while it's drying? If so, I guess I'll have to wait until I go home for Christmas and have access to a private garage to make the repair.

Thanks!