PREHEAT oven to 400°F; COMBINE 2 cups all-purpose flour, 1 1/2 teaspoons salt, 1 tablespoon sugar, 4 teaspoons baking powder and 1/4 teaspoon baking soda in a large mixing bowl; CUT in shortenings until mixture resembles coarse crumbs. STIR in 1 cup buttermilk just until a soft dough forms (dough will be very loose and sticky at this point). SPRINKLE flour over a large wooden board; TURN dough onto a floured board and knead gently 10 to 12 times or until no longer sticky, re-flouring board as necessary while kneading. DIVIDE dough in half; GENTLY pat or roll each half into an 8-inch circle 1/2-inch thick. CUT out biscuits – pressing straight down – with a 2-inch biscuit cutter. REFORM scraps, working it as little as possible and continue cutting. PLACE cut biscuits on an ungreased baking sheet with edges barely touching; BRUSH tops of the biscuits with whole milk. BAKE for 15 minutes, or until golden brown. IMMEDIATELY brush biscuits with margarine (or butter) after baking.