I cannot give you a "one size fits all" answer, only can tell you what our ideas are. When do you show, what are the barn conditions, in particular, what temperature do you expect in your show stalls and show ring. ????
Personally, we do not keep our cooler that cold. The idea is we keep ours around 60 and have no problem growing or keeping hair. If we can keep our show stalls around 80 with fans and rinsing several times a day, the cattle do not seem to "melt".
We wash outside before 7:30 when the temperature starts to rise. Whatever you do, do it for the cattle's comfort and be consistent. (A daily ritual) Good luck, just my 2 cents worth.