Steamed Chinese Buns

Name: Steamed Chinese Buns
Yield: Makes about 32 Servings
Ingredients: 1 1/2 cups warm water (105°F to 115°F); 3 1/4-ounce envelopes active dry yeast; 4 cups high-gluten flour; 1 1/4 cups all purpose flour plus additional for kneading; 1/4 cup sugar; 1 tablespoon salt; 4 tablespoons rendered duck fat,* melted, cooled slightly, divided; Nonstick vegetable oil spray