So This was the original sketch that got us going on the Cough Syrup For Your Offspring
We wanted to keep things really rough and expressive, almost Russ Mills-esque. So I converted a photo of Chris to black and white and digitally painted in some scribbles to act a base. From there I printed out the image on two sheets of printer paper and mounted them to a scrap piece of illustration board. I went over a few spots with quill and India ink so get some of the smaller details. Then I quickly threw down some black and white gauche with a bristle brush to get some of the longer strokes established.
The reason I used gauche vs. acrylic or oils was to keep the turnaround time short. Gauche is a very opaque medium to work with and very fast drying so the whole process took maybe an hour or so.