I have an animation of a fluid emitter creating a spray through a field of wheat created by using Paint Effects. My problem is that the Paint Effects render over the top of the rendered fluid and not smoothly within the created field (the spray is animated to be passing through the field).
That's odd, i know paint effects is a post processes but was pretty sure it retained z-depth info. Well off the top of my head i would render them out in seperate passes and composite them in Shake of After Effects. Or you could also maybe convert the paint effects to polys but looking at your scene that might get really heavy.