I would say it depends on the sprayer. I don't mist my tank, but that is because I regulate humidity in other ways. Every frog I've ever seen comes out when it rains, because that is the best time to do extended exploring I suppose. I feel misting the frogs is probably fine just as long as the sprayer doesn't developer excess pressure. Might be better to use a watering can? It would be more like rain and have almost zero pressure, the volume might be a bit high though... I'd like to see the scientific evidence that missing is harmful, we are taking about amphibians, not dessert lizards or spiders...