Note: The scene was created, rendered and posted without post processing using the default vray options with the "Raw reflection" and "Specular" passes enabled under VFB channels.
After using vray on sketchup for a while, I discovered that "trace reflections" option under V-ray material editor - Options adversely affects render time. As a solution, for materials that I'd rather show the specularity only, like grasses and trees, I normally turn this off.
With trace reflections ON : Took 33 minutes
With trace reflections OFF : Took 16 minutes
By default, the skatter grass bundles have this option turned on (https://drive.google.com/open?id=0B3XXDAl-vV8FbDRYeWFnOGRZVWc) and every time I open a scene on sketchup, I have to turn it off. Every time. Somehow, once the proxies are reloaded, the option is always on. I have tried a local solution, that is, editing the grass from the library, first the actual SU model, then saving it as a proxy to replace the original but it seems to stop vray from rendering the particular grass.
I would thus propose that we have the bundled grasses have this option turned off by default, or even an option on the skatter dialog that turns it off or on as per user preference.
NB, with trace reflections I contend that the grass does look better, but with a little photoshop using the specular channel, the no-trace reflections grass looks stunning too IMHO. The question is, are I willing to take twice the time to produce the grassy bits? Nope! P.S. It took me an hour+ to do this...and here is the no-trace reflections image after applying the specular channel on photoshop (Screen blend mode only) - https://drive.google.com/file/d/0B3XXDAl-vV8FQVBCdG1hTXVCVHM/view?usp=sharing