I found this great 1950 ad/article on baking a layer cake in one pan. It is an ad for Cut-Rite Waxed Paper, and it includes some basic instructions by Dione Lucas, an English chef and the first female to graduate from Le Cordon Bleu. I doubt all that many women at this time knew who she was or the significance of her accomplishments, but she had a very interesting career, including being the first woman to be featured in a cooking show on television, that being To The Queen's Taste, 1948 - 1949. I guess this was as close as one got to product endorsement contracts back then.
Here is how Dione Lucas explained How to Bake a Layer Cake in One Pan, from True Story Magazine, December 1950.
1. Use your favorite cake recipe. To make the cake easier to turn out, line the bottom of a square cake pan with waxed through Cut-Rite and grease. Now pour in half your cake batter.
2. Separate layers with 2 sheets of extra-heavy Cut-Rite as wide as the pan and 2 inches longer. Grease sheets on both sides. Place on batter crosswise to form neat corners. Now just pour in the remaining batter.
3. When cake is done, turn out of pan. separate layers by simply taking hold of each sheet of Cut-Rite and pulling layers apart. Remove wax paper and you're ready to ice.
Sounds easy enough. Or, you could just go buy a second pan. I'm just sayin'.