I used to breed in small deli cups, I opened one small hole on each cup to allow a little bit or air exchange, the thing is I can´t tell you exactly how much to moist because I did it by "finger", sometimes I didn´t had to moist it again during the whole time, sometimes I had to moist it once, I usually checked my eggs once a week (I mean, I looked at them every day trough the incubator window, but I opened it to check the moisture once a week, I just touched the vermiculite, sometimes it was getting a bit too dry and I misted it again, carefully so I wouldn´t wet the eggs... I had a very high hatch rate like this