Whisk together 8 cups water with 1/4 cup of the salt. Place the sliced potatoes into the water-and-salt solution and let soak for at least 20 minutes. After they have soaked, dry thoroughly on a paper towels or dish towels.
Heat the oil a large Dutch oven to 350 degrees F.
In a spice grinder, combine the buttermilk powder, onion powder, garlic powder, sugar, dill and the remaining 1 teaspoon salt. Grind into a homogeneous powder.
In handful-size batches, fry the potatoes until they just turn golden brown, 2 to 3 minutes. Toss immediately in a large bowl with some of the spice mixture. Then place them on a baking sheet and sprinkle them again with some of the spice mixture.
Hold them in semi-airtight container for a few days, if you can stand it that long.