Nothing wrong with the method, but perhaps not good for oil-based paint. The human breath has a lot of humidity in it, which doesn't mix well with oil. Water-based paints would be OK, I would think.
Regarding Earl Scheib, I had a car repainted by his crew in Denver when I was in high school. I did all the prep work, block sanding the body, etc. The paint looked fine for a few months, and then started to peel off. It wasn't covered under their warranty; that only covered 'fading', which it did not last long enough to do. I believe the cost at Earl Scheib at that time (late 1970s) was around $79.
I resanded the whole car and had Maaco spray it again. This time it cost me $149 as I recall. Looked great, no issues with peeling.
However, in both cases, there were runs in the paint. I actually had to explain to the managers in both cases what a RUN was and why it was bad. They acted like they had never seen one before, didn't know how it could happen, didn't want to respray, etc. At Maaco, I showed it to the manager and he claimed he could not see it. A RUN! Big huge drip right down the side of the fender and he claimed it was not there. I was a kid then and didn't know how to handle it. As an adult, I'd grab him by the neck and run his face over it and ask if he could see it now.