When Im developing a composition, I typically work from three or four reference photos Ive taken myself. I combine these sources into a graphite-pencil drawing, called a cartoon, done on vellum, a high quality tracing paper.
Before I transfer the drawing to my support, I turn the cartoon facedown and coat the backside with Conte crayon—gray if Im transferring to a light-colored support or white if Im transferring to a dark support. Then I smear the Conte with tissue to imbed it into the vellum, and blow off the remaining dust into a trash receptacle. Next I position the cartoon face up over my support, and use a very sharp 9H pencil and slight pressure to trace over the lines of the drawing. Periodically, I stop and lift the vellum to see how the lines are transferring, making any necessary adjustments in pressure.