When I do a cover for a company I usually make three layouts that one of them is the one I'm gonna do. So after I create a better sketch of it on a plain paper 20lb and then I put it on top of the good paper Briston 100lb and with the help of my lightbox I trace it so as to have clean and smooth lines.
On this video you'll watch how I do the sketch after the approval and before the final lines.