Living Downunder, we have found the best way to keep the cockers cool is through their feet - we wet a towel, ring it out well and place it on the bottom of their cage/crate/trolley - or occasionally wipe their paws with it.
If we are in the ring standing in the sun, I wet a terry cloth nappy and take this into the ring with me - draping over the ring fence when needed - it's vey fiunny going in for Group specials on a warm day to see all the gundogs with their wet towels and nappies on them and the humans red and hot ! I notice at some shows they have 'cool' pads - similar to the ones used for injuries.
