Just click "start new drawing" ( or whatever the link says, i just forgot
) and I just looked at a picture reference of him, and started coloring.I made the muscles and slight shading stand out by using the airbrush tool and choosing a darker color, then just add where you think it belongs.
good luck!EDIT: Oh, and click file, 'save drawing' and it'll let you save and post it to the fourm.
Then you can just copy the page address and post it back here on Smincy's wonderful lineart.
