Bad Dolly

Just a little Dolly extermination, they are quite the menace...

Question - I tried using a particle emitter and deflectors for the corridor shot, to bounce particles off the wall and floor, but found it crazy hard to line up floor and wall planes on a 2d background. is there an easier way to get the plane in the right place with the emitter in 3d space, so it looks like things are bouncing off the walls/floor?