Bump and color data in a single brush? Is there any way to paint onto a bump map and diffuse map at the same time, so that the strokes match up? Like a multi-layer brush that uses a greyscale texture for the bump layer and a color texture for the diffuse color?

Here's a rough sculpt to demonstrate what I'm imagining:



The GIF above shows how such a brush could be made. The black and white height map would be the displacement brush, transferring its greyscale data to the bump map texture and the green one would transfer its color data to the diffuse map texture.

The resulting brush images:





Making the brush is one thing, but is it possible to use such a brush?
Blender only paints to one image at a time.

One solution may be to set the texture brush mapping to stencil and align them visually. If your brush textures align and you don't move the 3dview then the two textures will just line up after you change brush settings and active layers.

When you enable stencil mapping, the texture is overlaid on the 3dview. Use  RMB to move the texture into place, &#8679; Shift  RMB to scale and &#9096; Ctrl  RMB to rotate, then use  LMB to paint it onto your texture image.