I love what your making. Are you planning to to release it to the public? This would be awesome with a live viewport shader, although I don't know how you could extract the flow map in real-time.
Awesome stuff Mattias! Are you just using the buildNormals stuff you mentioned before or doing some Math like getting the normals of the vertices being hit and aiming them in the direction the brush is moving (factoring in intensity and falloff)