Here are the steps that I use to create a typical illustration. This illustration was created for a promotional postcard. For this page, I photographed the interim steps, but the final picture was scanned.
I sketch out the different characters, compose on the computer, then create a final pencil sketch (this is on regular ol’ 11 X 17 office paper).
I used a light box to trace the drawing onto a piece of vellum-surface bristol using a 4H pencil (i.e., very faint lines). I used a mixture of white and sepia acrylic ink applied with a #2 round brush to outline the drawing.
I mixed a sepia and black acrylic ink wash to put in the shadows. I like using the acrylics, because they don’t lift or bleed through the watercolor and gouache.
I blocked in the colors using watercolor. I paint broad areas with a #4 flat brush.
I added more highlights, shadows, and colors with gouache (I also like the opacity that gouache gives to certain areas).
I finished the illustration with some line work and other details using a #2 round brush. For this picture, I mostly used sepia ink, but also some terracotta and a sepia/white mix.
Here’s a detail from the final illustration.