I have two paths for doing my comics: Analog-Digital and Digital. When I start out in analog, I usually just do the sketch with a .3 mil mechanical pencil and regular leads as they erase easily, have high contrast (are easier to see) and scan well. Then, I ink digitally. I am looking for non-repro blue leads for my mechanical pencil, because I currently use non-repro Prsimacolor pencils if I intend to ink by hand and it`s a pain to sharpen them every two lines. Then I can scan in the inking without the sketchwork.
Lately I`ve been totally digital, sketching directly on my standard comic layout with my Wacom tablet. Despite the fourth panel, I sketched this comic by hand and I think I will move more towards sketching by hand. I like sketching by hand better, but having a digital canvas allows me to resize, drag, add canvas and erase instantly and on the fly. Those are some compelling reasons for digital sketching. Plus, once I have my inks the sketches are for all practical puroses irrelevant. I keep them around because I like looking at them, but they serve no further production purpose.