I also demonstrated this technique with gimp a while back (dear lord this was almost 5 years ago.....)
http://www.cartographersguild.com/sh...wing-Buildings

Of course, with the current unstable gimp 2.7.x and the upcoming 2.8 stable, you don't need to create a special angular GIH brush, as the brush dynamics let you map angle to direction and jitter on size.

-Rob A>