Paint systems vary plant to plant, and manufacturer to manufacturer. Can't generalize. And OEM paint is different from aftermarket repair paint.
I spent some years in an auto plant environment, and the paint system where I worked changed from Dupont to PPG, and the paint was totally different, and not for EPA reasons. One of the paint systems required high heat to cross-link, and the other did not. Again, different.
My memory is failing me, so I can't remember all the details, but I do remember that the first coating was a dip into the E-coat tank (gray). Next, a color matched primer. This was not high build, just a splash of color, and base layer for the color to be added next. Then the base coat of color was added. The hood, doors, hatch, were in place, to assure the color texture was consistent, and the metallic laid down the same, panel to panel. Last, clear.