1. With a pastry brush or paper towel, brush shortening evenly over the bottom of the pan, taking care not to leave any uncoated shiny spots. When you're greasing the sides and corners of the pan, turn the pan on that end so you can better see what you're doing. You don't have to go all the way to the top of the pan.
2. When the pan is completely greased, sprinkle a couple of spoonfuls of all-purpose flour into the bottom of it.
3. To distribute the flour evenly over the pan, hold it on one edge and rap the other with your free hand. The flour will "skate" over the greased surface and stick to it. When the pan bottom is coated, tilt the pan, tapping it to move the flour over the sides. Tap out any extra flour into the sink.