So here's my process for creating the cover to Defenders #3.
First I do a little sketch that I send to Marvel for approval - a 5 x 7" marker drawing done in my sketchbook then colored in Photoshop CS3.
Next, I pencil at 11 x17 on 2 Ply Bristol Board.
Rachel then inks with a brush and ink.
First pass at coloring (in Photoshop).
Final pass at coloring after notes from Marvel.