Basically, what I found was that it is pretty common to bake the cakes a few days before and freeze them while still warm. This locks in the moisture, makes the cake easier to fill/ice, and saves you some time as you get closer to the big day. Definitely not an essential step, but made absolute sense for me. Here was the timeline I used (and loved!):
In this case the wedding is on a Friday...
Monday - bake the cake. Once cooled enough to handle (as warm as you can stand) level the tops and turn cakes out onto a couple layers of plastic wrap. Wrap tightly, adding a third layer if needed, then cover with foil and place each layer in a gallon ziplock bag. Place in the freezer immediately to seal in the moisture.
Tuesday - fill the cake. Remove cake layers from the freezer and spread filling between them. Stack the cakes, then recover in plastic and foil. Return to the freezer.
Wednesday (or as it ended up, Thursday morning)- make the buttercream and crumb coat the cake. The crumb coating is essential to prevent crumbs ending up in your final icing layer. Apply a very thin layer of icing on sides and top of the cake. (Freezing the cake also helps with this step since the cake is hard and not as fragile. Plus the buttercream will harden quickly). Using a small amount of buttercream, adhere bottom of cake to a cake board cut to fit the cake, cover with plastic wrap, and place cake in the fridge. Cake will begin to slowly thaw.
Thursday - final coat of buttercream & decorations. This should be done at least an hour or two after the crumb coat to give it time to set. Be sure to put a nice thick layer of buttercream on this time and decorate as desired. Unless you are using fondant, return cake to the fridge until delivery time. If you are doing multiple layers, decide if you are going to put the cake together before or after delivery. Be sure to have dowels and cake boards ready to stack the cakes.
I was thrilled with how well it held up, even after hours of setting out on a warm and humid Indiana day. I will definitely be using this method again (and soon) for my brother's groom's cake in a couple of weeks. Hopefully this will help you with all of your wedding/ birthday/ holiday/ any day celebration cakes. It was definitely an eye opener to me and so much easier and more manageable to do one step at a time.