Thanks to BOTH of you for the tips! Both options are beneficial in their own way. I personally am still partial to the saran wrap on top of the screen, this way I think you get the best of both worlds, as it retains moisture and doesn't reflect heat. Also I've noticed using damp towels that as KMG said, it will start to rust the lid--but more importantly, the towels start to smell funny after a while, almost like mildew or an old dish sponge?

So I recommend saran wrap, but again, it's all about personal preference. Thanks again everyone for your input!