I think your process is fine as is to be honest. Only thing is you don't seem to reevaluate form after you are done cleaning it up, you may want to look into it, although its def. not needed for this particular piece.
I'm pretty sure everyone works by the same model, first sketch with a pencil then either scan and outline or just play sketch n computer, add colors, clean it p, add detail, reevaluate colors, reevaluate detail, reevaluate colors and so on and so forth until the piece looks good.
That being said, here is an aweosme website I found in someones sig while browing Pixelation today. The guys is pretty good, and has awesome step by step animations.
http://www.retinaleclipse.com/pixelart.htmlTry and find more step by step animations like that, or just go to any of the featured threads. Those are the ones where people make most progress on their drawings.
Oh and finally, try to find more techniques to use. I see you already make good use of dithering and I think creative dithering (? not sure if you do this one), try sub-pixel animation and other crazy things, I'm honestly not any good yet but that's what I'm planning to do next to improve, well when I say "next" I mean after I learn how to find proper colors, how to do textures, etc /sigh.