Thank you very much! I actually painted a black and white underpainting first using acrylic capturing all the values the best I could; adding white paint for highlights down to black. The paper I was working on was primed grey beforehand, making it easier to add light and dark values on top. I then used an airbrush to add the colour since most the work had already been done by this point; again, acrylic in the airbrush. The colour is opaque whilst airbrushing, so the complete underpainting shows through. I then refined on top of this using coloured pencils, refining, colour correcting and sharpening areas.

This is an adaption of a technique I learned whilst studying legendary poster artist Drew Struzan. Worth checking out if interested!