I have a magicfly/Janoel 12, too, and it is a bit tricky to get the humidity level to stay steady. I took a cap from an empty spice container (the red ones, McCormick?) and put it underneath the top tray, and poured tiny amounts of water directly into it. I got a four pack of digital thermometer/hygrometers...they are cheap and so I don't think they can be calibrated, and certainly not in ice/boiling water. But I watched them for a couple days on my counter and my thermostat and they all read the same temperature that my thermostat read so I figured...good enough! I've kept the humidity around 30% throughout incubation and got 13% average weightloss by Day 16, so at least the ones I received seem to be fairly accurate.
For lockdown (tomorrow) I plan to put a damp paper towel in to help keep the humidity higher during the hatch.