if you look carefully at Lincoln on a US dollar you see that what is important for a 'hand-made' effect is that the etch lines follow the contours of the face, ie the bone structure

you cannot get that automatically with a computer because that information is not in 2D drawing or photograph, all you have is light and shade

the example Mike posted is a fair example of following the light and shade, but if you want a true 'hand-made' effect it needs to follow the bone structure and you need to tell the computer where that is and that means work

if anyone knows a shortcut I'm all ears...