You can use backburner to network render the prepass. You can also use DR with your local machine to calculate every frame for the prepass. The good thing about the prepass setting is, you don’t have to check the “Don’t Render final image” check box. All you have to do is enable, Animation (prepass) and it automatically won’t render the final image. This way all you have to do is, set up the Animation prepass, send it to backburner.
Then switch to Animation (rendering) set the file name to the .vrmap filename, then just send that to backburner. Don’t worry if max says there’s a job with the same output name, the prepass won’t generate rendered images. When you send the animation one to backburner, set a Dependency so that the Animation (render) job won’t render until the prepass job is finished.
Hope that makes sense.