I'm in the same boat as some of you, near Melbourne.
Before last weeks crazy heat i ran two systems with misters.
1 on the broody coop, where the chickens were confined to, its misters on the open walls and sprinklers on the roof and western wall. It was much better in there than my house spoilt things. This one needs a timer to come on for a short period then off, something like on for 2 minutes off for 15. Things got a bit wet, but everyone survived.
The other ran through the fig tree, then over another 2 coops in different areas. I would use this one in the morning for half an hour to wet everything down, i didnt use it in the afternoon when they were sitting under the fig tree cause they would run out.
It was all very cheap, think about $70 total from bunnings and a bit of sunburn putting it up.
I'll try post a photo but i seem to be failing to do that recently... It just doesn't work.