Once the preliminary pencil sketch is done, I grab a pencil with a softer, darker lead (usually an HB) and clean up the pencil drawing, putting in definite line, detail and some shadow. It's still rather sketchy, but that's because I generally finish up in ink. If this was going to be a pencil final, I'd put far more detail into it with shading. (Though, with a four-inch drawing, the matter of detail is going to be limited anyway.)