Dzieki my friend!
Yep, exactly as you said. First the major shapes in lightened tones of the basic colour to get an idea how they'll look (as you can see on the right), then working the forms in darker tones, building up to dark Green (not Black) for the darkest shadows.
In saying that, I did forget that golden rule when doing the lower left area and need to revive it. Straight Black as a wash to create shadow is never a good idea, whether paintings or models. It's a 'dead' colour which is too contrast and pales everything around, often killing the whole effect. Much better to use a mix of the colour being applied to with either Black, dark Grey or dark Brown for shading.