Its actually not that difficult. The 8B pencil is my friend, but you could achieve the same effect with charcoal, albeit messier and greater chance of smudging.
Thanks! I hate charcoal for the smudging reason- I've tried using fixative spray but it kind of yellows the paper. So for know I've been going 8B then I smooth it over with an HB but it takes forever. Somehow it never turns out as smooth as yours. What kind of strokes do you use- circular, straight?
Straight when doing background, circular when working in shading, and straight in some shading as well. Its about which brand pencil you're using. I use staedtler's 8B in specific as it lacks the sheen that other pencils give off.