Paint the background, not too solidly, in its tone relation to the cast, half closing your eyes to judge its depths ; and cover all the canvas up to the outline of the cast.
Now take your middle tone—that is, the general aspect of the cast—the tone next in value to the higher lights, and paint fairly thinly with a good size brush over the whole surface of the drawing,
leaving essential indications intact, and right up to the background, so that the edges melt. Now place your study beside, or in line under, the cast, referring to your glass, to see what you may have to do to get the relation of the general tone of the cast and background still nearer ; for now that your canvas is completely covered, you are in a better position to judge these things.
This is an important stage and settles for you the key of tone that you will maintain throughout. Now paint the shadows and draw them in definite shapes (with a brush of moderate size, not by any means a small one), comparing their values either lighter or darker, or perhaps in places similar to the background. Ignore all marked passages of reflected light in the shadows, and let them merely be felt in the general tone where they come, but not outlined. Nothing gives a more commonplace or cut-up aspect than the marked reflections, on which the beginner insists. If you will only look at them, your eyes nearly closed, you will see how much less definite they really are than they look at first sight.