Script-Fu -> Sketch -> Pencil sketch BW
This is a non-adjustable script (just option to merge layers or not when complete.)
pencil-sketch.scm by Jeff Trefftzs
but with a custom pattern and very specific, altered settings
It does an exceptional job of sketching smaller portraits for web and phone distribution -- also does a nice job opn graphics...
a big plus for me !
Script-FU > Sketch > Pencil Sketch BW