There is an extensive tutorial in the manual for how to create PBR shaders. It uses the "Sanctum Art Kitty" that is included in Core Content, because that has so many different types of surfaces in it (glass, plastic, fabric, metal, etc etc). 

There are examples for both Physical Surface and CYcles/Principled

Starts here:

Using PBR Maps with Poser

(You don't need to download the content from psoersoftware.com as it states in that topic, they were added to core content and should be in your Included runtime.)