From The Practice of Tempera Painting:
"The outlines and modeling are to be worked up on the white gesso surface in ink. The shadows may be done exactly as on tinted paper, with a thin wash of ink on an almost dry brush, gradually strengthening the tone by the addition of more ink, and producing a smoothly modeled shadow. Or they can be wrought more boldly, with hatching strokes like a pen drawing, or any other way the painter pleases. This ink drawing on the gesso acts as an underpainting, and has a profound effect on the modeling of the shadows on the actual painting with colors. It should be carried out with about as much accuracy and finish as the painter wishes to bestow upon the final painting. Color may be used instead of ink, if you prefer. The drawing may be done with tempered pigment, black or any color, as long as the half tone and shadow values are established at least as strongly as they are to be painted."
Here's the transfer onto gesso with Saral. (Not one of my better scans but the tone is still light.) I'm working the lines over with silverpoint and then going after shadows. Now just how does one create a range of values with a little piece of fine silver? I soon found that quick and jumpy spasms make a scratchy mess. Smooth graceful lines followed by small and lightly applied circular strokes are effective. Hatching and crosshatching make for a convincing and controllable value range.
I don't expect to take the metalpoint very far, just enough to guide me with the color, but wouldn't a well done silverpoint be a fine long term project...
Thompson, Daniel V. Jr. The Practice of Tempera Painting. New York. Dover Publications. 1962. (Yale University Press. 1936.) p. 49.