LogInGaël Kerchenbaum and the TexturingXYZ team have recently shared a tutorial on creating procedural skin.
The new guide discusses how to work on procedural skin using Mari and maps from TexturingXYZ. Basically, you can use the same workflow for creating skin maps. The artist discussed a proper setup that can be used for different creatures.
One of the keys here is using Mari's possibilities. First, you need to learn about a Material node which can let you quickly texture several assets, "without the need of re-creating your complete nodes-tree." The latest Mari allows users to treat Material as Smart-Materials by using Geo-channels.
You can find the full written guide on using TexturingXYZ maps and Mari's features here.