I always bake 2 days ahead.
I learned this from someone else here (don't remember who lol) - I overfill my pans just a little, that way, immediately after they come out, I cut off the top, leveling it right with the top of the pan. Then flip onto saran wrap and wrap twice. Yes, I do this piping hot. However, you MUST get all of that top "skin/crust" off or else it WILL get gummy (had this happen before), hence the overfilling. Just make cake balls with the rest.
I leave the cake on the counter. Let cool, wrapped on a wire rack then when cool, move it off the rack. I even freeze if I'm terribly desperate (although I don't like to). I took a cake out of my freezer on Saturday morning that I baked Thurs (wanted to hide it from DH since it was for our anniversary...it didn't stay hidden long lol)....left it on the counter and started decorating Sunday evening. It was still moist yesterday (the day) and today when I munched on some more of it. Incredibly moist!
Also, icing and covering with fondant helps lock in the moisture. Don't refrigerate fondant cakes. Not good for them (I forget why). I leave mine at room temp (in the summer I keep the a/c on) without a problem. And I use an all butter BC.