I'm not a big fan of either steaming water or wiping water onto the wood ... oh, I know, both methods are used and the proponents of each say they've had no problems doing it that way, but ...
Having worked in a place that built fine wooden furniture, I had it pretty thoroughly drummed into me to NOT get wood wet ... it will tend to raise the grain and can easily cause damage.
I've very successfully followed the method of putting an open container of distilled water into the humidor, closing the lid and waiting about a week .. then, use a calibrated hygrometer to check the box and if it is low, close the lid and let it go a few more days ...
care must be taken to avoid spilling water from the open container and the water should be replenished as (if) necessary during that period.
It takes a little longer, but hey ...