The material editor can be opened from the toolbar or by going to Plugins> V-Ray for SketchUp> Material Editor. With the right mouse button (RMB), click on the "Scene Materials" materials can be imported, added new or purged unused materials. A material can based on four layer types - emissive, reflection, diffuse and refraction. A layer type can contain unlimited layers. All layers are in order like placed on the material from top to down. The default material contain one active diffuse layer. Additional layers can be placed per RMB click on a layer type and choosing Add New Layer. The preview window dosn't show the current selected material, it show the last rendered preview.
All example renderings are done in full adaptive mode and noisethreshold 0.02 (good preview quality).
* Screenshot of the V-Ray material editor:
proceed on reading at ASGVIS webpage(very long tutorial you won't regret it)
this is more of a strengthening the knowledge on how the materials were assign and work in vray. A bit confusing for newbies even for me...(who are especially lazy to read this whole)