I sometimes prepare a dummy for submission, first by creating a storyboard. A storyboard consists of thumbnail sketches plotting out the 32 pages of the picture book. After the manuscript is accepted, it's time to move on to the artwork. Conceptualization is fun. Writing and storyboarding are liberating and oftentimes, agonizing.
Painting is quiet and methodical.
There's a lot of sketching and re-sketching, using tracing paper and lightboxes to help me configure a composition. Finishing 32 pages of artwork, plus a cover, can take me 3 months. I use watercolor, water-soluble pencils and pen on hot or cold pressed watercolor block. Packaging 3 months of finished artwork and sending it off is always a little stressful. Then it takes a couple of months, sometimes more, for the publisher to finish the product.