Black and Tan (pic heavy)

Here is a pictorial of Apple Barrel Country Tan (inexpensive acrylic craft paint) layered over black primer.  The tan is diluted to minimize acrylic binder texture on drying, as miniature painting ideally should be.

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So after 12 coats of tan, the coverage is "good, not great."  There are still visible areas where the coloration is inconsistent.  This is a good demonstration of what goes into a very smooth paint job; I certainly don't have the patience to paint entire models like this for gameplay.  I think the misnomer here is thinking of each of these steps as "coats" like painting a wall would get coats.  When you are painting with very thin coats, one area is drying rapidly while you are working on an adjacent area.  I took pains here to go over each area only once between photos.  In practice I would be going back to the areas that had incomplete coverage almost immediately after finishing a nearly area.  The paint should be thin enough that it dries pretty much as you watch.

I might repeat this exercise with a foundation paint over black primer and see if the result is significantly different.