First, cover your hands with either some disposable gloves or a Ziploc bag.
Then, use your covered hands to spread some room temperature butter generously along the entire inside of the baking pan. Make sure to coat all the corners and sides. You should achieve an even coating with no chunks of fat leftover.
If desired, use a small sifter to evenly distribute a small amount of flour across the inside of the coated pan. Then turn the pan over and tap out any excess flour.
Finally, pour your prepared batter into the greased pan and bake away!