I've seen several tutorials for ganaching cakes, most of which refer to the upside down method, spreading the ganache with a bakers blade evenly between two cake boards. I tried the method for the first time tonight with fair success. Aside from the fact I misjudged the amount of ganache needed for a small 6" cake, the only real problem was the removal of the top cake board. Despite using a warm offset spatula to separate the board from the ganached surface,the board peeled off every bit of ganache from the top.
Here's my question - before folks started using 2 cake boards, wouldn't ganache have been smoothed out much like buttercream? Why couldn't I just hold the blade perpendicular to the bottom board, exercising great care to keep the blade straight up and down as I move around the cake? Why the additional step of adding the second cake board, which, even with the pros, leaves divots and air bubbles after it has been removed?