You will get a wide variety of answers. None of them wrong, it will be what works for each person in their own situation.
My horses are home. They are 20 & 21 so I cater to them a little more.
Up until today, we have had horrible humidity with our dew points in the high 70's and the heat index 105-108.
I have those big green tub fans from Tractor Supply in the barn. They are on heavy duty outdoor timers.
Both horses have a fan they can stand directly in front of. By early afternoon the fans are pushing hot air. But between the fans and the barn being dark, the horses quickly learned the flies don't bother them.
Plus they have all the hay they want while they are in there.
My horses come in at night so, the fans are set to shut off at 1:30 AM and come on at 6:45 AM.
They do brave the heat to graze and will be a sweaty mess by sunset. I will also cold hose them down at night, and take a wash cloth to them to get the sweat off; paying attention to get their nether areas and inner back legs wiped clean.
If your new horse has an issue with baths, for now just concentrate on her chest, neck, shoulders, heart girth area. I use a nozzle with a shower head and turn it to "shower".
The purpose being to get her cooled down. Then stick her in front of the fan
Corporal posted before I was finished, lollol
Ditto plenty of FRESH water and a salt block. My horse are separated because one has some tendon issues. They both have two 20 gallon tubs of water and two 50 lb white salt blocks.
I fill the tubs every morning and they get cleaned as needed. About every other day in our humidity. No ice is right
. However cold it comes out of the spigot if perfect