We have had great luck just sorting the calves off the cows during the daytime and putting them in the showbarn under the fans and misters. The calves run loose in the pen with a pan of feed always available. My sorting the young calves off, it also gives you an opportunity to halter them up occasionally, and also rinse them once in a while. They are no different than any other showcalf you are getting ready for the fall shows.
Shaving their heads, tails, and any other extra hair on their tops and necks can also help keep the calves cooler, thus growing more hair sooner.