Yes a mop job is just that when done incorrectly. Before anything is done ,no matter how you perceive the repair in its final stage, never use sand paper as the first line of attack. The paint surface is full of particles, car wax for one, that if not removed prior to sanding will become imbedded in the microscopic sanding scratches. This will become exacerbated by the use of grease and wax remover sending those particles deep into the surface. The result is called solvent pop. Not what you want to appear on your newly applied primer or top coat. I am old school when it comes to prep. Wash and water rinse, dry the area. Use the wax remover in small areas, wipe on and wipe off, do not allow it to sit on the surface. The top coat is the easy part, the prep done correctly will give you the best chance of getting the results you imagine.
THANK YOU Kyle for posting this (and thanks to ChrisFix too for making it look so do-able)!! I got a nasty rock chip in the front fender of my '54 Bentley (yes, really) and was getting ready to just live with it when this article came along. I spent less than $30 on paint and sanding kits from Amazon, spent 3 weekends sanding, painting, wet sanding, re-painting, re-sanding... I'm really not even done but already you'd need a magnifying glass, a bright LED light, and me pointing it out before you could find it. The blending isn't perfect because the old paint is faded, but at least it's super-dark black against slightly less dark black. Before, it was glaring bright bare metal against black. You could have seen it with your eyes closed.
And before you scream at me... half the paint on the car is original, and looks it. The rest of the paint is a mix of professional repaint and driveway rattle-can job. There are plenty of other, bigger flaws that will keep it from getting "best in show" any time soon. It's a driver, and now I can drive it again.
Paint me happy and hella proud that I did it myself!