It’s life. Beyond putting a cheap outdoor thermometer/hygrometer in the first hatch or two, I haven’t really worried much about humidity. I’ld have to almost write a book to describe my incubator in detail to get quality help and advice.
Normally I have done what many call a dry hatch just using ambient room humidity for 18 days and adding water to raise the humidity at lockdown.
I’ve pretty well decided that I’m going to have to get a reasonable quality remote hygrometer before next season to work all the kinks out.
To raise the humidity I have two large double cake pans sitting underneath my eggs, yet on top of my heat source. The pans can have water added without opening up the incubator. I have a couple of sponges in each pan to help the water evaporate some. Next step would be to add aquarium air stones to the pans and a small aquarium air pump outside of the incubator.
Biggest issue is needing to be able to monitor humidity. In the past, I haven’t had problems, so why fix something that’s not broken - except now it’s broken.
For temperature, I use an amazon digital thermostat that can be set to a tenth of a degree. I set it by making a few egg size water balloons and then checking them with an older human mercury thermometer. For safety I have an additional digital thermometer. Even though neither is accurate, I write the temp readings for both down when I get the water balloons at 99.5. The thermostat has held true even from year to year.
The incubator is well insulated and has a heat sink, so that if the door is opened to candle, the temperature will bounce back up pretty quick, or if the power goes out the eggs would be alright for a while. I have a generator if needed.