The best way to quickly get a mask from selection?

[Monkeybrother]

Hi. I use the "RenderMask" script when rendering in V-Ray, but the latest version of that script seems to lock up Corona/Max (I have to force close it). I installed the Corona toolbar and tried the "RenderSelectionMask", but it takes a while to render, where RenderMask is almost instantaneous.

So, what is the best way to get a quick mask from Corona? I know about the "mask" render element, but pretty often I need to get a mask of some detail after rendering.