Research in natural media painting has produced impressive images, but those results have not been adopted by commercial applications to date because of the heavy demands of industrial painting workflows. In this paper, we present a new 3D brush model with associated algorithms for stroke generation and bidirectional paint transfer that is suitable for professional use. Our model can reproduce arbitrary brush tip shapes and can be used to generate raster or vector output, none of which was possible in previous simulations. This is achieved by an efficient formulation of bristle behaviors as strand dynamics in a non-inertial reference frame. To demonstrate the robustness and flexibility of our approach, we have integrated our model into major commercial painting and vector editing applications and given it to professional artists to evaluate.