Now that both cake batters are finished, you'll be alternately adding each flavor to each of your three cake pans. I suggest starting with 8 ounces of vanilla cake batter in each pan, followed by 8 ounces of chocolate cake batter in each pan, for a total of about 16 ounces of batter in each pan. If you're using 6-inch pans, use 6 ounces of vanilla, followed by 6 ounces of chocolate. When I add the second cake batter flavor to each pan, I use a spoon to make dollops of cake batter. Once all the batter is added to the three cake pans, take a toothpick and make swirls in the batter.