Here are some process shots from the painting I did for the cover of Ghost Factory magazine.
I was working on a piece of relatively toothy illustration board with Golden acrylics, (Titanium White, and Mars Black) and FW acrylic ink, for the line-work, and to mix into my blacks instead of water.Initially, I laid down a wash of diluted ink, to give myself a mid-tone to work off of, and so that I could lay down the basic shapes in white, rather than a darker tone.
With the basic shapes estalished in truly rough drags of white acrylic, I go in for some definition with indiluted FW ink and a 6 round watercolor brush. Mainly, I am establishing the form of the ships that will be the focal point of the illustration, but I also take the opportunity to play around with a texture on the ocean. I can always paint it over (which is exactly what I end up doing.)
With the forms of the ships established, I fill in the ships once more with white acrylic, to take take down the severity of the ink line, then lay in the shadow shapes in a slightly darker than midtone grey. I always like to work near the middle of my value range at first, so that I can save the blackest blacks (and lightest lights) for where they might be needed. (In my experience, it is easier to make a piece darker than lighter.
I paint the background second, starting with the light circle, and cleaning painting the dark margin last. As each plane of paint masks the one under it, I take the opportunity to clean up the contours, and sometimes correct the outline of shapes.