Steven hit it right on the head. You don't gotta worry about the substrate being too wet with the substrateless method. The reason you're getting condensation is because the temperatures inside the tub are different than on the outside of the tub. This is the reason you want to have the tubs ready to go and in the incubator a few days before you expect to get eggs. Once the temperature stabilizes inside the tub you shouldn't have much of a problem with condensation.