I accidently rubbed my wheelbarrow against my tailgate when it was down and put a deep 4" long scratch right down into the primer. :-(

What the best way to fix this?

In my previous life, I've tried filling a scratch on my beater car with touchup paint that came in a tiny bottle that looks like my wife's nail polish, but the outcome looked terrible to say the least.

I'll be going into the deal later this week for some warranty work, so I havne't asked yet, but I seem to remember seeing some reference to them selling touchup paint in a spray. Would this work better? I have an airbrush set that I'm tempted to try to fill the scratch with several layers of paint and then polish. Would that work also?