i usually walk my horse out until his chest is cool (or at leas warm depending on how much time i have) and then untack, and if needed i bathe him graze him in the sun until he is dry (not really any specific amount of time)
At the end of all my rides, hard or not, I let them walk out around my property for about 10 minutes. I then always hose them down after but that obviously depends on how cold it where you live. I live in Florida so its always hot lol!
you just have to let your horse walk for about 15 minutes. you don't need to ride them hard at all. give the a loose rein or hop off. loosen the girth too