This is how I was able to make it work, hope it helps.

Just copy the imported .vrmat settings to the proxy material.

https://youtu.be/TJWDnucxBLA

HEY...!! This tutorial is exactly as mine, I did it on july, but mine includes v-ray tutorial too...!!!!!!!!

Check it out on http://forum.gfxdomain.com/others-tutorials/5391-xfrog-plants-tutorial-sketchup-v-ray-spanish-only.html