Creaming butter with a wooden spoon does work, believe it or not. The rough surface of the wood helps to incorporate air into the butter and sugar mixture by creating uneven surfaces within the butter as it folds onto itself.
From a box sold in San Antonio, Texas.
Shortbread (2 pans)
1 cup butter (let stand to soften)
1/2 cup plus 2 Tbsp. powdered sugar
2 cups flour
Heat oven to 300 deg. F. In a medium bowl, beat butter with a wooden spoon. When soft and smooth, add sugar and beat until light and fluffy. Add flour all at once and mix thoroughly.
Form dough into a ball and divide in half. With hands, press evenly over bottom of round pie or cake pan. Mark lightly into wedges with a knife.
Bake 45 to 50 minutes. Cool pan on rack and cut into wedges as marked (will just lightly brown).