Thank you!
I just made use of the particles system to recreate the moss. Although truth be told, I did not achieve what I really intended at the beginning. I was looking for a more… soaked-looking material, as though it rained. I still have a couple of ideas that might help me out with that.
(see: Mossy rock)
So no complex node/material composition, I am afraid I do not have that level of skill to accomplish such a deed