Use the Quick Texture Mixer
to combine the two textures. This is done by holding down the left
mouse button at theicon,
dragging it to the target texture and dropping it there. Theicon
is located on each of the Texture
Do this now: Drag the mixer icon from gravel bump texture to the
brown carbon texture. After this a menu will open, containing the
different mixing modes. Choose the Emboss Medium mode. See
how the brown carbon texture gets depth.
Repeat the procedure, but choose the Variate mode this time
to darken the bumps.