I would try soaking a piece in warm water. I wouldn't run the water, just put one piece in a BIG bowl of cold water and soak it. The salt will come out, but how evenly is tough to say. the other issue he will have is that the smoking preserves fish partly because it dries it out. Rehydrating the fish will negate that. He may have to soak it then dry it again in an oven. I would also suggest changing the water out from time to time, say over the course of an hour. As the water absorbs the salt, it becomes less effective at absorbing additional salt. So several shorter soaking in fresh cool water will be more effective.
Wish him good luck with the process. It's a shot in the dark at best, but if he can figure out how to do it on a couple of sample pieces it might be worth scaling it up to the whole batch.