Cakes of just b/c on top of eachother without messing them up?
When you stack the cakes, you ice the cakes on their own cake boards. Then you can put them in the freezer for few minutes and using a big spatular you can take it and put it on the cake.
Hope it make sence.
But I highly recommend Sugarshack's Buttercream DVD if you want to see her doing it so perfectly. Here is the link to her blog,
That's what I do too - refrigerate/freeze and only stack cakes whose frosting is solid. I also leave the dowels sticking up from the bottom tier so that when I set my upper tier on it, it sinks to the bottom tier and I don't mess up the frosting on either cake. This is especially helpful for fondant covered cakes that don't get refrigerated. Just make sure you push your dowels all the way to the bottom and then pull up, otherwise you could some that refuse to sink in!