Decanting is perfect for big amounts or for snuff you intend to keep for a long time. I keep most everyday snuff in its original container inside a closed biscuit tin and store in a dark and cool cupboard, I seal the tins with isolating tape also and make sure its replaced once it no longer sticks well (the white one used by plumbers, the electrical one is also fine).
In the event snuff dries out simply re-hydrate it over night with pharmaceutical grade purified water.
I just add some drops in the corner, do not mix it, allow the snuff to absorb it, takes about 24hours.
Be careful not to add to much, its better to repeat the process than exaggerate and have your snuff become mud).