Here's a video of my painting process, some color studies, and sketches that are an integral part of how I iterate to a final product. I use Maya or Rhino models to make vehicles and spaces; I use those renderings to start paintings. When designing, I make hundreds of silhouettes. Before painting interiors, I make sure that my perspective grids like up correctly to my vanishing points. I make around four to ten layout sketches and four to six color studies to make sure I hone in on a consistent mood or theme. I do material studies, like for mushrooms, metal, or snow, and of course, I doodle the whole time. Drawing is thinking, after all.