Dave,
In all honesty, the process should not vary. The factory masked off certain areas and then painted. Sometimes the masking and prep work was not the best and over spray got where it was not intended for. This would explain why there are similarities yet differences from each vehicle to the next regardless of body style. You could have two challengers one right after the other and depending when someones break was, two totally different people could paint those two vehicles even though they are right next to each other in the assembly line.
You pretty much cited a perfect example of this with the inspection marks and trying to replicate someones "signature". It could take you 2000 times to try and replicate something that someone did within seconds back in the day. And to be honest, my signature has changed from when I started signing my checks back when I was 18 to the scribble I do today!