2D motion blur is a post process and works with every render. 3D motion blur happens at render time and is FireFly only. The two are completely independent and there's no need to use both of them simultaneously. Pick one. 3D motion blur is more expensive, but also a lot more precise. It will work correctly through transparencies and object occlusions. It simluates a real camera shutter that you can control through the shutter open/close parms of the camera. 3D motion blur will show up in a single frame and is turned on/off through the "3d motion blur" checkbox in the FireFly options. 2D motion blur needs to be applied after rendering by selectiung "Motion Blur document" in the render menu for a single frame or checking the "2D motion blur" checkbox in the movie settings when rendering a movie. In any case, if you don't see the amount of blur that you expect, chances are that there's not enough motion in the scene. If you want a single frame with a superhero showing up only as a streak across the scene, make sure that it crosses the entire scene in that one frame. If it moves only by one inch per frame, it will blur not more than one inch per frame.