I don't think 75 days is necessarily to far out. It's just a matter if you have the time to put into it each day. Putting ice water in the swamp cooler or foggers is fine, cause it does help drop the temp in the cool barn. The idea with ice water though is to chill the hide. If you just put it in a spray bottle, you would have to make sure that you get enough on him to get down to the skin and in an amount that will chill the calf. I have heard some people use the chest freezer for an ice chest and they pump the water out of it to soak the calf. That would work really well, but if you have more than 1 calf, you might need more than 1 freezer. I guess the poor man's way of doing it would be how I was taught which is to fill a couple of 5 gallon buckets with water, put them in the chest freezer in the morning and by mid-afternoon you pull one out and just dip your rice root in the water and start brushing away. Simple yet effective. I don't do it because I have access to some cold water out of an irrigation ditch. We can pull a calf out and soak him with the hose for 15 minutes and he will actually shiver - and then the hair grows.
I think the common theme here with most of the successful show people is that they chill the calf with water and they brush- and they do it a lot. However you choose to do it is up to your imagination.