Alan,
You can PM your email I can send you his blend file with the node setup or you might be able to download it from the webpage where he shared it with me.
https://blenderartists.org/forum/sho...etchbook/page5
The way he built it, its nested/grouped in 4 levels. Enclosing screen captures of the different groups. He is using the ambient occlusion along with a power math modifier to capture detail up front and blur the detail as you get further along the model. I tried using a logarithmic math modifier and seemed to capture more detail but the power modifier seemed to be smoother.