[Gimp-user] How to do XnSketch-like effects ?

[u4000 <forums gimpusers com>]

There is such application - XnSketch, but it's proprietary and probably doesn't
allow to sell edited photos. But it produces amazing effects, for instanece
SketchBW effect makes provides very authentic effect of hand-drawn picture (like
it would really be drawn by hand). Aslo Pencil effect is very beautiful.
If there any plugins or tutorial which allow to get the same qaulity ?

-- 
u4000 (via www.gimpusers.com/forums)