My second try in Mudbox came out to be much more successful than the former one. Although I still can see mistakes I've done. I will need to straighten the bridge of his nose and pull it a bit up.

One of the things I found irritating was that I couldn't adjust textures properly. Skin painted with them was in an impossible grey tint or looked bruised, so I decided to use custom brushes available in the program and paint the sculpture by an eye. My basic brushes were speckled and dust particle like brushes. Generally I could use effectively only B&W brushes.