My opinion on a cooler, If you have the resources to build and run one, cost is not a factor then yes they are a great tool for hair. We did not have one and did not get the hair our friends did with one. The kids with the cooler put in just as much time rinsing blowing and grooming (twice a day during school year, and 3 times oncethe school year ended) Our fair is in July, our calves went in the barn the last week end of March, same as the calves that went into the cooler. They had 4 inch yak hair we had 1 1/2 -2 inch decent hair.
It is not a short cut to avoid work, they rinsed, chilled (pumped water out of a box freezer that was just above freezing) and blew the cattle out, they did all this in the cool room, so it actually took longer to get them blown out, they had a wash rack in the cool room.
Cooler or not the more work you put in the better the hair, A solid routine that is followed daily is key, everyone does it different but it is going to take time everyday to really acheave good hair.
It may not be exact but basically what my sons did for hair
April- June (add a mid day rinse once school year ends)
5:00 Halter, rinse (after first week calves were at the gate ready to come in)
5:15 Comb hair up and put behind fans go eat breakfast
5:45 Blow out completely, add product, feed
6:30 Go get ready for school
7:00 Pull feed pans muck stall
7:30 Go to school
15:30 Tie head up, muck stall, rice root brush, blow.
16:30 Rinse
16:45 Blow out
17:30 Feed
18:00 Pull pans, muck stall, blow and apply product to hair.
18:30 Eat dinner work on home work
19:45 Rice root brush and blow, fill hay feeder, work on setting up, kick out
20:15 Muck stall, fluff bedding, wet bedding down
20:30 Call it a day
The order may have changed some days and depending on the heat and sun they got kicked out later sometimes