I'm using blender guru's method ( http://www.blenderguru.com/articles/how-to-render-a-complex-scene-without-crashing/) of separating my scene into different layers for rendering so that I can use one of my GPU's that only has 3GB of VRAM, BUT, since I have both an NVIDIA and an AMD in my machine, and a cpu, I am running 3 instances of blender all at the same time, each using a different part of the machine to render out an animation. I am ALSO rendering using the CPU's of a few different machines. All of them point to a dropbox folder so they can all see which frames have been render or are being rendered.
My problem is compositing the layers once they've been rendered.
In the Blender Guru article, he renders in one instance of blender and opens the rendered file that blender detects in the previous renders function. I don't have that luxury. Is there a way for me to open my rendered files after the fact for compositing?