Hi again, Bill. Water a LOT, now! You truly can't give pumpkins, squash or melons too much water in hot weather as long as they have good drainage. Since you planted yours on a hill, I'm sure your drainage is fine.
Your pumpkins absolutely need to be watered every day during hot weather unless it rains an inch or more. A passing thunderstorm rarely rains enough for your big, demanding plants like pumpkins. Their vines sometimes grow a foot or more per day, and when they're sizing up the fruit, that takes a ton of water, too. If your plants are on a hill, yes, water the whole hill deeply - half an hour or more if you're using a sprinkler. The roots don't go straight down from the plant they fan out into the soil to a surprising distance from the plant.
For fertilizer, I use Osmocote for Fruit and Vegetables. It's widely available at nurseries, and the big box stores. The analysis is 14-14-14 which is known as a "balanced" fertilizer. You might want to give your County Extension service a quick call or e-mail to ask their recommendations because different soils need different analysis sometimes. But I use this same fert in my sandy garden in Florida, and in my daughter's clay soil in Utah. She (we, that is) grows pumpkins too, by the way. They water their vegetable garden an hour every morning with an automatic micro-sprinkler system that I installed for them. It's a desert, there though. Very dry air and very hot in summer.
Yes, by all means try the milk mixture to prevent the fungal blight from spreading. It won't remove what is already there, but it will stop it from reproducing and infecting any more leaves. If it doesn't work for you there are a few other fungicides you can try, but be absolutely sure they are rated for use on edibles before you spray anything! Also, remove any dead leaves that have the powdery mildew on them, bag them and throw out in the trash, not on your compost. You don't want any more airborne spores flying around than you can help.
It's pretty important to try to keep the foliage dry to prevent things like powdery mildew. But as long as your plants have good space around them for air movement, and you aren't watering them in the evening then leaving them wet all night, the preventive measures you take with the milk spray or other fungicide should stop that problem.
