Do not recommend applying water directly to the wood, especially in cheap chinese humidors - the veneer is about the thickness of paper (which is the reason this method seems to work without ill effect) and behind it is pressboard (which absorbs moisture readily, but will quickly deform-faster than solid wood). This construction is why they are even able to dry out. A solid constructed box will not dry out if left closed.
Another reason not to use these cheap Chinese humidors.
But back to your question. One: do not apply water directly to the wood. There are no shortcuts especially with this type of construction. If you want a shortcut, buy Bovedas and put them and your cigars in a tupperware container and be done. If you want some cedar in there, buy yourself some Spanish Cedar trimmings off ebay and toss em in.
I give away those Chinese humidors to friends/family that are interested in cigars. BUT.... before I do, I tear them apart, put a sheet of lexan in the floor (factory is 1/8" pressboard over felt, extremely porous), line the sides with 1/4" Spanish cedar, and replace the "seal" with an actual fitted set of sealing slats made from 1/4" Spanish cedar.
I know of one that I rebuilt that was neglected for a year, with a single Boveda, and was still sitting at 60% (with a crunchy Boveda) at a year and a month when I asked about it.
As an experiment, I threw a 65 Boveda in a factory stock cheapo humidor to see how long before it dried up. Just a little over two months and it was crispy.
Buy tupperware and Bovedas and stop worrying about maintaining your humidors. Or, spend the cash (or time) to buy (or build) a quality wooden humidor.