If you get a ragged edge turn up the spacing on the brush, and make sure it's 100% opaque. Then if you want it to follow the direction of the brush, set the angle jitter to "direction", and it should follow the direction of your stroke.
"I must not fear. Fear is the mind-killer. Fear is the little-death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain."
--- Frank Herbert, Dune - Bene Gesserit Litany Against Fear
Check out my Sketchbook! Critique and Criticism welcomed.