i started with a squashed angled regular brush with no dynamics turned on. working in monochome on a multiply layer i blocked out the major light and dark using 3 main values. i then added a layer set to "color" and started adding the hues. from here i started introducing different brushes and different opacity settings on another layer set to normal, the basic work flow being from opaque and crisp to glazing in using a vareity of textural brushes. i'm seriously considering laying this out more throughly in book form.