Hey Greg, Not a problem, Never a problem.... Yeah the thin coats are a bit frustrating cuz they dont lay down a coating you can see at first, and several coats are required just to begin to see the results. Thats why I go thin like that, so as to have the graduated (in density) appearance that such a stain would have. Exhaust soot would not have a "hard line"pattern, and would graduate from denser to almost un noticable.
Just remember to be patient and build up little at a time, remembering to dry in between coats with a hair drier if desired, that will speed up the process and allow you to see errors or progress as you go coat by coat.
As far as enamels go... Rarely do I ever use enamels any more, and none were used on this build, The reason is that with todays new and improved acrylics they smell, clean, adjust, and apply better IMO then enamels. They even have acrylics now for automotive applications that are way easier to apply then enamels or urithanes .
I have some acrylic candy shades that I use to do Motorcycle designs like tanks and such that cant be beat and are MUCH easier to use then any enamel I've ever tried. That includes lacquers which at one time was the best paint on the market.
Sorry I'm getting long winded again, but the only non acrylics I use any more are the occasional artist oils mixed (Thinned) with paint thinner, or the lacquer "metalizing" paints from Model Master. Alot of the specialty paints (other then RLM and such colors) I use I order from tcpglobal.com . They are the best source for House of Color brand paints. There is no custom paint that you could ever think of that they couldn't supply. enamel, lacquer, urethanes, and yes acrylics.
Doug