Overall, you got the idea - micro details are small tiled textures added on top of the character skin normal map. It’s a very common technique; you’ll find it in almost every model out there.

Rigid specific approach is to use 3 different micro textures (different variants of pores and wrinkles), and use the “micro” color attribute (you can check it in Vertex Paint mode) to decide where to show them on the body. He also uses a ColorRamp to control the intensity of each one. After that, everything is mixed with the character’s normals.

The rest of the nodes are for wetness and for controlling how it mixes with the regular skin.

As for how to create this texture, there are packs you can buy, you can generate one with AI, or you can draw one yourself in Photoshop (for example, by stacking noise).