The shot glass (or any container that can hold water) will take longer, and the wiping down is a short cut.
Here are some pro's and con's of each
Cons
Shot glass:
1 - takes a while to season, I believe around 2 days to maybe a month, and some people have never been able to properly season due to inferior seals on their humidor, but that is another story altogether
Wiping:
1 - possibility of raising the wood grain
2 - possibility of water stains on the interior
3 - if using a non-sterile sponge or towel, foreign deposits might get embedded into the porous wood and damage the smoking of any cigar placed in the humidor
Pros
Shot glass:
1 - none of the cons of the wiping down.
Wiping:
1 - can season a humidor faster than getting served at your DMV.
On a side note, did you properly test and calibrate (if possible) your analog hygrometer that came with the humidor (if any). Use that first (after properly calibrated with salt slury or the test kit), and then compare it to the digital hygrometer. Hope this helps, and if there is anything else a more experienced member can add, it will be greatly appreciated by all.
edit - analog, not analogue
