I think the trouble some have is thinking of a single particle floating around doing loodyloops through the slits. This probably isnt a perfect picture but feynman diagrams describe it best for me. I think of a pool of plastic balls. Say somewhere in the middle a ball moves in a circle or whatever. Now you have this motion dispersing out where it could go through any number of slits only to arrive at the wall as a packet of energy. This isnt perfect but I just substitute quanta of energy for the plastic balls and the motion for the wave.
