Eric Brian
The processing is only a minute or so . . .
This is the start point - works well with buildings and portraits - I have done it with the kids watching - mostly by keystrokes having taken their picture - downloaded to laptop and then printed on to watercolour paper torn out of artist pad - parents bought results for charity. Duplicate - desaturate - duplicate again - invert - chose colour dodge as layer style (should look white) chose gaussian blur (high setting) or "Other -minimum" (one or two pixel setting). Flatten image and increase contrast in layers. Experiment and colourise with a soft low percentage history brush (Experiment with modes) and erase margins to suit.
So far prints of images like this have made about £200 for charity and used as logos for local churches