I cannot claim authorship for this technique but it creates a lovely pen and wash effect which I wanted to share
Duplicate your photograph (Ctl J)
Use filters-stylise-glowing edges
You want nice sharp, well defined edges so play about until you like the result (I used Edge width 8 Edge Brightness 6 and smoothness 11)
Convert to black and white by your favourite method (you will have white lines on a black bg at this point)
Invert the picture (ctl I) to give you black lines on white.
Create a duplicate of your original photograph and drag it to the top of you layers stack
Use blending modes to create the sort of effect you want (I used multiply)
I then used the eraser to remove some of the top photograph to reveal the lines underneath, making the picture look unfinished.