I think cool fresh water and shade is all chickens need in my area. It has been over 100 a couple of times so far with very high humidity and they do not seem to mind. I used misters in the past but my girls do not like the mist.
I have a shaded pen, 20x12 with another 20x5 in full sun plus a small enclosed shed they sleep and lay in. When it is this hot they still go into sunny areas throughout the midday for dust-baths and just to hang out in the sun. They do take a couple naps throughout the day though.
I have a large pond and notice all the very large wild birds out in the heat as well. Herons, egrets,etc... My girls are Astro-whites, ( australorp, leghorn cross). Perhaps the white colors keep them cooler? Anyway, I keep the fresh cool water coming and ensure they have shade if they choose to be in it. They seem very happy and content.
I have been in chicken factories before with 1000's of birds in big warehouses being speed grown for markets... now those places are sweltering. (That's when I started raising my own for meat...just terrible). I am no chicken expert but birds are resistant in extreme heat and cold from what I have seen, I do like to keep my girls happy though.