Guys, thanks for your encouragement – keeps me painting.
CCMATTY – I basically use the Army Painter wash painting technique, and then highlight afterwards* with white dry brushing.
At the root of the process (the basic operating principle), is that semi-diluted washes can best contrast against light backgrounds – so that the washes can create color shading if "splashed" over white primer, or even over other light colors, like tans, lt. blues, lt. greys, etc.. This is the OPPOSITE technique of painting over black primer, because black doesn't allow lighter washes to contrast against the already darkened background.
That's the most important part of understanding "shading", "washing", even "inks" style painting – you must have a lighter background to contrast against – and this allows "gradients" of color shading to occur. The color gradient process occurs because watery washes like to flow into cracks, crevices, seams, and folds on figures – you don't need to "push" washes into cracks like with opaque paints, washes naturally want to flow into these low spots – doing the gradient shading all by themselves, by collecting into sculpted areas and intensifying color there when they dry.
The whole process is to allow the sculpted detail on figures to draw the colored washes along the lines and into the low spots, and to naturally direct the flow of color where it'll darken more in the recesses and less on the high spots.
This is allowing the figure to do a lot of the painting and shading for you…..because washes flow, but paints don't.
I give praise and credit to Army Painter for designing and marketing their Tone washes years ago, which are consistent mixes that colorize over white primer or other light colors. Furthermore, multiple layers of their wash Tones can be applied over themselves to intensify (darken) the primary color (gradient). Citadel tried to duplicate the AP Tones' technique I think, with their Contrast line, but created washes far too intense in color IMO, and that are more like inks, than washes.
So the "technique" I use is founded on thinking your figurine starts out as if it's a white canvas, and you're applying colors upon the white to colorize desired areas. Of course, a figure isn't a flat canvas, it has curves and etched details that'll capture the washes applied on top, and bring the liquid down into the sculpted cracks and crevices – therefore self-shading details, and create variations in the same color applied, those "gradients" of the same wash color, and doing this automatically (instead of trying to do this by applying multiple layers of successively-lighter colors of opaque paint).
There's other quick-applied techniques to create further contrast or highlighting – I wash the final, completed figures overall with a mixed dilution of Dark Tone and Vallejo Glaze Medium (6 Glaze to 1 drop of Dark Tone). When brushed over a completely painted figure, and left to dry overnight, the subtle "line" shading in the sculpted recesses does even more of the "pop" rendering.
*I mentioned highlighting with white dry brushing above (which is merely pulling out some of that white canvas background again, but "on top" of some of the sculpted detail – to get additional contrast/gradient affect). The *star* here is because this white dry brushing can be applied over a coat of opaque painted area too, like over trousers painted [Union] lt. blue, or [Rebel] tan or grey, for instance……..then, I apply the complimentary colored wash. The end result is that the white dry brushed areas create even more highlighting when the wash is applied over the figure's painted trouser color, and so the white dry brushing looks less stark to the eye, if it had been applied as the last process.
I hope this portrays the basic wash [AP Tone] process I use, with some of my own way of thinking about it. :)
Oh, one last comment – I paint for the tabletop, not for the up-close shots. The somewhat exaggerated lighting effects of this washing and highlighting technique shows through at the 3-4 ft. viewpoint pretty well.