Heat oven to 400°F. In a large bowl, whisk together flour, baking powder, sugar and salt.
Add shortening with a pastry blender or potato masher, cutting until shortening is in very small pieces. Stir in milk.
Gather dough together, kneading slightly if dry. Pat out to 1/2-inch thickness, and cut out as many biscuits as possible with a 2-3/4-inch round biscuit cutter. Gently gather scraps together and repeat patting and cutting, for a total of 8 biscuits. Transfer to an ungreased baking sheet. Brush biscuits with butter.
Bake biscuits at 400°F for 14 minutes, until risen and golden on top. Cool slightly before serving.