I think the misters are a great idea! I've seen a lot of people on the AZ threads swear by them. I definitely would NOT give them any corn in the heat. There's something in the way their bodies process corn that generates extra heat. We only give them corn in the winter when we're trying to keep them warm. During the spring, summer & fall we give them kale, cold watermelon, chopped grapes & chilled pomegranate seeds (mostly watermelon because it keeps them cool AND hydrated.) In addition to refilling the waters twice a day, I also like to keep an extra one full of electrolytes out there. (My favorite is the Rooster Booster brand with extra vitamins because it doesn't have that weird color & smell that some of the others do.) If your chickens are afraid of the frozen water bottles, try putting them inside their drinking water. It will help keep the water cooler longer. Good luck you guys!
https://www.amazon.com/Rooster-Boos...id=1498203702&sr=8-1&keywords=rooster+booster
https://www.amazon.com/Rooster-Boos...id=1498203702&sr=8-1&keywords=rooster+booster