as long as the substrate was from a tank thats currently running and cycled, it will definatly help. put the sand or gravel into new, clean pantyhose and put it by the intake if the filter. it will force some of the water to go through the hose, and in-turn carry the bacteria to the filter media.
*this is something i was told to do a long time ago when establishing a new tank, and having gravel from another. wether it works or not, i dont know, but ive never had an experience that would say no. its always seemed to speed up the cycling process for me if i cant spare some bioo-media