So this is what I've decided upon for my final character aesthetic. I'm using two different techniques but i think they compliment each other.
The basic technique for colouring my man is this;
re-sized raw jpegs, paint over in photoshop on a new layer using a multiply blend. Using this layer to give a solid outline delete the unwanted exterior on the original photo. then duplicate this layer, threshold and overlay on top of the image using multiply to give the defined black lines.
Below is an example of a combination of this technique and finished painted dog frames ( I haven't painted the background yet)