Looks like you could achieve the effect with a Paper Mode type rendering (no textures, only shadows + geometry) and a lot of Photoshop texture overlays.

Best way to learn this is trial & error. Now go forth and fail for a while.

various blending modes in photoshop with paper textures downloaded from cg textures

Yeah these still look they were done as a (high-) standard vray render, with a lot of textured post-editing in photoshop

Try rendering to 32bit float and then gamma correct back to linear space with a really flat / midtone weighted gamma response curve.

Thanks for the responses, will have a play and see what I come up with.