This node setup use a colorfull texture as input and replace the mapped colors with materials.

This has some advantages because unlike stacked stencil textures you can edit the material assignment in one single image.

I use this because even if i can brush and draw arround in blender i cannot draw different maps (diffuse, specular) on the same stroke.

With this approach i just draw with a color and replace them later with a complex material.

Also creating texture patterns in vector programms becomes pretty easy

because of the simplification to simple colors.

Feel free to use and tweak it.

Maybe someone has a better example texture to share.