Experimenting sketchy shading

Once more following Artur Guptill’s “Sketching and Rendering in Pencil”, I somehow tried to applied the sketchy way of rendering shading he describes in Chapter IV, Part I.
I used a single pencil, 2b Mars Lumograph, although it’s recommended to use different grades for finished pieces. I guess this is fine since mine was more of an experiment. I setup a pretty simple still life with old, rusty metal objects:
(notice the camera angle was slightly different from mine when I was drawing).
As you can see from my notes on the side, it took me roughly 3 hours. More to get the drawing accurate, to be honest, since the shading was pretty quick and probably not careful enough.