I think I saw him explaining how he does his sketches, and doodles on his tumblr once. He basically just takes his linework that he did traditionally and puts it on a transparency layer and copies it to make the linework more refined and darker. He then edits out that extra stuff to make it cleaner, but he leaves a couple of sketchy stuff in because he likes the grit.
So much awesome! I love these designs, practical and yet awesome!
Also, sorry to be a bother, but I saw a comic of yours posted somewhere, ages ago now, where a girl was asked by a small monster representing "the legion" what she thought of the new spiky teeth? Might I ask which gallery that comic is contained in and if there is more?