I do the same when it gets super hot. I spray down the magnolia tree for them. Good thinking.I would melt fast, I just went out, dumped the days water and filled with cold water, then I , from the run gate, sprayed the tree trunk which made splash/mist- sprayed the far east side, I didnt get where the big hens were standing wet I didnt want them to run and over exert themselves- it is 98 in the run, the chicks liked the coolness from the water when I was done and they are not panting.
I'll go out at 4 and do it again