I agree with wifezilla with the average humidity. I live in central texas where the average humidity is ZERO unless it rains...which is once a month or so lately... If I don't spray/mist my eggs every couple of hours the humidity goes to ZERO, even with all the plugs in my bators!
In places like Ohio and gerogia, where the humidity rarely, if ever, drops below 50%, you should be fine dry incubating.
My hatch is STILL going on...I have one straggler who has decided the interior of the egg is a fine place to live and grow lol. They were all set the same day...but three days of pipping/zipping/hatching and I have SIX pure cayugas, and three blue swedish/rouen mix ducks, and the one straggler that is a rouen/pekin/swedish mix (i think).
The pilgrim goose eggs are due NOW and they're still rocking...PLEASE HATCH! lol
Next week...ANCONA DUCKS! My personal FAVORITE duck EVER!