I am glad that my tutorial is useful for you.
To Guest:
"How did you create the cracks?"
Here is workflow of the process:
1. I have used pen shown on the picture, and painted depth and specular
2. In start position pen radius was 2.63, depth=0.73 and specular=0.08. From this position I moved pen down to next point, where pen radius was increased to 3.44 and depth=1.00. Than I have moved pen down and in third point pen radius was set to 4.15.
3. Than I repeat the same procedure in backward direction and in result we have crack. After calculation of occlusion it will become more contrast.