When you have a wet type the evaporating water makes the job. The wet incubator should be without holes. In dry type you should use closed containers with moist substrate. I never had any problems with humidity, could you describe your problem more precise? What type of incubator do you have?
The humidity in the incubator should not matter if you have the correct water to vermiculite(or perlite) ratio. I personally do a 1:1 ratio and put no holes in the container. I open the containers twice a week for air exchange.
There is no need to put humidity in the incubator only in the deli cup or whatever you are using for the eggs which should be 1:1 ration water and vermiculite.thats where the humidity should be