I also never understood how people can make such good looking materials. I mean i would basically have an idea how to layer it, but every single attempt will immediately fail due to an unexpected behaviour of the material editor.
With the incredible amount of free textures and tools available one would think that there are hundreds of examples available. Insert alerting failing sound
You have to buy it. Or spend weeks if not months to figure it by yourself. Knowledge is free they say, now mix your own antibiotics 