With those incubators you have to set up a good amount of time before you put a clutch in. How it works is the water is heated to a particular temp and water holds its temp pretty well. Humidity is kept up well in those types of incubators but I'd air it out a bit everyday.
Yeah they work pretty well. I use to hatch box and wood turtle eggs in a homemade incubator that way. Except I used a 10 gallon aquarium. Super easy to make on your own.