A great tutorial over at Tuts+ covers the process of compositing V-Ray renderlayers into a final image. Much more comprehensive than simply stacking the layers, they get into several post-production techniques that realy make the image pop.
In this tutorial Ahmed Fathi takes a look at how to composite together V-ray render layers using blending-modes and masks in Photoshop. Once completed, this process allows you to change or tweak any aspect of your image in seconds without having to re-render a thing! Ahmed also covers a few extra post production techniques such as Chromatic Aberration and Depth Of Field, as well as how to emulate a Cross-processed look.
