Any tips on repairing scratches in paint

[vip808]

I'm having a hard time trying to cover a scratch in my door. It's about an 1 1/2" long with part of the metal showing with the edges of the scratch looking like primer. I tried using GM touch up paint with the Langka repair kit but the paint covering the edges comes off. I've tried painting then using 2000 wet sand and polish but the paint is so thin on the Hummer that it looks like I'm making the edges of the scratch worse.
Are there any body shop experts here willing to give out any shop secrets on how to repair scratches? Do I need to re-paint the whole door?
Any help would be greatly appreciated.