Because baking is such an exact science, I never double a recipe. When I am making a cake, I place all the dry ingredients in a zippy bag. If I am going to be making more than one cake, (such as two wreath cakes tomorrow) I repeat the same process. Each cake is treated and measured as an individual cake.
When I am ready to start baking, I place the dry ingredients in a mixer bowl, then add the liquids called for in the recipe. I also made the frosting for each cake separately. Each batch is in a separate bowl, just waiting to meet up with the cake.
My first husband was a trained pastry chef. He had a booklet that he wrote all his own recipes in. They were for 25 or more people. When I read them, I compared his recipes with tried and true ones in The Joy Of Cooking. I did the math and saw that when broken down, to an individual dish or dessert, there would be like 1/4 cups of flour left over, 1 ounce of milk, etc.
Start with your dry ingredients first. They are the most difficult items that require the most attention. Get a box of zippy bags and when you are ready to start making the cakes, do so one at a time.
That doesn't mean you have to bake them one at a time. The most I put into my oven is three. I tend to make triple layered cakes.
Illegitimi non carborundum!
I don't want my last words to be, "I wish I had spent more time doing housework"