Let's start with the finished drawing by Xubucheng. (Edit) Blog reader ZS has generously translated the Chinese notes in the book, which I'll show in bold after each step, followed by my own observations about what he seems to be doing.
1B. Use simple straight lines to mark out the shape/contour of the head, locking in the basic positions of the eyes, nose and mouth and ears. 35 minutes."
(My observation) In the the first step he doesn't copy contours, nor does he place spots. His framework is built from nearly straight line segments bounding important lines at the edges of the form.
He's also looking within the form for big plane changes (brow, cheek, chin) and for feature placement. Since this is an upshot, the lines for the brow, eyes, bottom of the nose and mouth are parallel, slanting downward in perspective. The ear and nose are roughed out in a few simple lines. These lines are drawn with controlled sweeping movements of the arm.
2. "Once the position of the features are determined, use shadow boundaries, projection lines, perspective lines and knowledge of head anatomy to further detail out the form of the features.
This kind of thinking—using arcs or gently curving line segments—is carried a lot further. Now he's more concerned with smaller plane changes. He's doing a lot of cross-checking at this stage to compare alignments. By the way, I believe each of these drawings was made separately for the purpose of the demo; I don't believe they're actually from the same sequence.
3. "Once the features have taken form, use shapes of light and shadow to delineate/differentiate the values, thereby achieving clear and accurate form and overall completion of the drawing. [ Trans. Note: I think he means overall coverage and composition of the picture, all that is left is detailing.] (45 minutes)."
In the penultimate stage, the planes are defined in terms of tone, drawn with parallel lines and a slight amount of smudging.
(Final stage--see first image in post) 4. "While in the process of drawing, always remember to compare the value relationship, structural relationship of the features, taking notes of the prominent/striking features on the face, and constant cross-checking and measurement until the portrait is complete."
(65 minutes)(total time 3 hours)
With the structure of shape, line, tone, and form established, he can resolve the smaller nuances to arrive at the drawing you saw at the opening of the post.
So there you go, Charles, and thanks for translating, ZS. If there's anyone out there trained in this method, I'd welcome your help in the comments.
Edit: To address Keith's question: "James, you said that you think these drawings were made separately for the purpose of demonstration. Can you elaborate on this?"
Keith, my impression was that the drawings didn't line up exactly. Rather than being a single drawing photographed in stages, my hunch was that it might rather be four separate drawings prepared in matched steps. They used to do it this way for art instruction books in the 1950s to save the hassle of having a professional copy camera setup in the studio. Below are two stages overlaid, so you can see for yourself.
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Russian Art Academy (interview with Professor Sergey Chubirko)