Re: Portrait sculpting speed/technique?
First I place my model on a turntable such that the center of rotation is through the center of her head. I mount the camera on a tripod and make eight photographs: front , back, 90° right, 90° left, and the four 45° positions between. I print them all the same size, large enough that I can view the clay head and trace the outlines of the photograph with the clay. A shot from directly above can prove useful too.
Then I place the armature on a turntable on my work table, mount the photograph so the clay head is between my eye and the photograph, and do the front view so that her head is shaped exactly like the front view photograph. Then I do the side views and the back view. Then the 45° views.
When those are exact, I am always amazed at how much the clay head already looks like the model's head.
Then I can use the live model to work on the details, without ever having to alter the shape of her head—it's already exact.