You aren't far from wrong. The problem with the Earl Scheib shops was that they had to push as many cars as they could through the place every day in order to turn a profit, and one of the shortcuts they chose was the prep work. Removing chrome, sanding, masking, etc., had to be done in 20 minutes. Period. Back in the 70s they used little clocks very much like those wind-up kitchen timers--wind it up, set it for 20 minutes, and start the prep work. When the timer went off they stopped the prep work and rolled the car(s) to a staging area adjacent to the paint booths whether the prep work had been completed or not. Anything not removed or masked got painted. They didn't care. "Whaddaya' expect for a hunnerd bucks?"