Beginning at the neck end of the bird, work your hand under the skin to loosen it. Start over the breast first, from the neck toward the tail. Then continue down both sides of the backbone to the thighs, and legs. Be careful not to pierce the skin.
Put 1 tablespoon of the seasoned butter mixture at a time under the skin at the breast and back. With a sliding motion, distribute the seasoned butter with your thumb as evenly as possible.