You can find out all the details of PxrSurface and its layerable parameters by visiting the Pixar Surface Materials.

For the easiest way to create a simple layered material, go to the RenderMan Menu and choose Create Material and select Pxr Layered Surface. We will create and network a layered material in the MAT pane.

PxrLayer

We can override the parameters in PxrSurface using the PxrLayer options. 

In this example, we set a green diffuse color in PxrSurface. Then we layer a PxrLayer node on top that has a cyan diffuse color. Note that one color covers the other, so we need to alter the Mixer node.

Green Diffuse Color in PxrSurface

Cyan Diffuse Color in PxrLayer

PxrLayer Mixer

We can combine layers using PxrLayerMixer. The mixer is where we decide where and how layers are mixed using masks. Below, patterns are connected to the Mask in the Mixer.

Diffuse Layers

We can layer specular, iridescence, and other illumination lobes.

Specular Layers

Iridescence Layers