Just a little bit about how I did my sketch.
Took around 15 mins and used only basic Photoshop filters/effects
First off I deleted red and blue channels, and converted to gray scale.
Then applied the following standard filters on duplicated base layers.
Photo copy (Sharpened once done)
Bas relief
Graphic pen x4 (one layer for each stroke direction)
Crosshatch (brush effect)
Then it's just a matter of playing with layer opacity on the last 3 above, to get the look you want