Mike,210bhp wrote: How many passes of top coat does that thickness represent?
My car had 2 coats of epoxy, then filler work, another 2 coats of epoxy, 2 coats of high build primer and then 3 coats of solid colour.....about 9 coats of paint in total. For metallic the final top coat would be substituted with 4 coats of base colour and 2 coats of clear lacquer.
Many people will do filler work directly on bare metal so you wouldn't have the initial epoxy coats although we like the extra protection.
Remember there's a lot of rubbing back in between and much of this is taken off in the process although plenty of solid topcoat, or lacquer, for final colour sanding.
Modern manufacturing techniques now allow for the bare minimum of paint to be applied and must save the industry a fortune; not an issue protection wise with modern galvanising although I wouldn't want to be a detailer trying to take back the orange peel you see on many new cars!