Press the “Make worn_edges” button to pre-render a mask around the edges of the mesh.
“Make Noise Worn_Edges” adds random noise to the edges mask.
You can then adjust the expansion of the affected area and its strength.
It is possible to invert the mask, reset the set values and enable help hints.
A useful trick is to set the Diffuse parameter to zero, so that the edges are only affected with normals and bumps.