Using saltwater to discharge a battery is a slow process
Imo, it's easier and much faster to simply run down the pack... either in a car or with a discharger of some sort.
Once it's been run down completely flat... (and you verify the voltage is basically at zero) you could even short the wire leads to keep it at zero during shipping. Or at least stick an alligator clip, etc.. on it overnight to keep it dumped. That's what the salt bath does.
A battery without any stored energy in it can't do any harm. It takes energy to get hot/smoke/start a fire.