I'm working on a project with material of blender. Since this morning, I tried to apply a texure where i can paint with, above another texture with brick. I want to be able to paint above the brick texture. I can't paint from the brick texture because on the shading node are applied color nodes that modify the base color of the brick.
You need to connect your textures to a Mix node with a mask image as the factor as shown below. Wherever you paint white, Texture 2 will show up, and wherever you paint black, Texture 1 will show up.