being its on the tailgate, IMHO, I would just pull it, sand it down, primer and repaint......it will be quicker, better and right the 1st time and a lot less work by comparison.

 

It's not just the tailgate, it's also the whole right side if you would read more carefully.

 

Those are some good key marks, someone really put in an effort! Unbelievable the idiots that are out there!

SScully an 2Stroked have you covered on advice, just take your time and allow each stage to cure long enough prior to moving on to sanding or the next step. Oxford White is pretty forgiving.

If you don't see desirable results, you may want to get an estimate and see what it would be through insurance to get fixed. a re-paint would be the best solution by the looks of the pics.