STEP BY STEP
I approached this drawing with a different technique. First, I did a sketchy line drawing...After that I used a [9h Derwent pencil] for the shadows. I kept everything very light...because the 9h pencil is a hard pencil...I wasn't able to smudge.
I also used a 5h and a 4h pencil...[9h being the lightest. 5h mid values. 4h dark values]
I also used a 9B pencil for the darkest values. I went from light to dark...[NOTE: I tweaked the contrast of the reference image to make it very light -High Contrast]
FINISHED DRAWING
[Pencils: 4H, 5H, 9H & 9B]