I think it would depend on a couple of factors, 1 is the material very dry or wet, and 2 how much or how little material you dump on the deck at once? I think the vibrator idea has it's uses(
) but I like the mechanical shaker because it will always shake no matter what. That's not to say that the material will pour through it though as the points above still apply they just won't stall it out. If time any money spent were no objects then I would build a trommel.