First, any time we take something out of its natural setting, like instead of a broody using an incubator, the rules change...
But really, it's simple... a heater in an incubator is a dry heat, a broody keeps her skin against the eggs for heat which is a moist heat... make sense? :)
Don't stress yourself, we gotta learn somehow... I've only spritzed later on when air cells weren't getting big enough in time...
Opposite effect hon... it only raises the humidity in the bator itself for a while, by the end of the day the humidity will be lower than it was before...