Place hash browns in a kitchen towel. Working over the sink, squeeze and wring out as much water as possible. Transfer the squeezed hash browns to a large bowl and stir in oil and 1/8 teaspoon each salt and pepper. Divide the mixture among the muffin cups, pressing it into the bottom and up the sides of each cup to form a crust. (There should be a solid layer in the bottom of the cup, but it's OK if the hash browns don't go completely up the sides.) Generously coat the hash browns with cooking spray.