There is now in Youtube ... mine second video about MyPaint.. http://www.youtube.com/watch?v=c4z1svphlJM
Btw. I try to do proper brush set for MyPaint.. now Mine "Tone" set is bit confusing... brush names are not correct and there is some misspellings .. like "Tones's" ... I have also done some more brushes.. like the old ... Liner Brush.. which is my opinion very useful.. it works faster than "shift" lines.