My two cents, a day late, dollar short. I use American Buttercream on all my cakes, wedding cakes included. (It’s what I was trained in) I live in a very hot and humid climate where the humidity can be over 80%, all summer long. I’ve developed my recipe to be a blend between Wilton’s High Humidity Buttercream and Sugar Shack’s buttercream recipe. (I use have butter, half crisco) I love watching Joshua John Russel on Man About Cake (youtube) and recently looked at his chocolate buttercream recipe. It’s an all butter buttercream which makes the icing set nicely in the fridge however, I don’t think it will crust. I don’t think you can use the Viva Paper Towel Method (which I do on all my cakes) That’s my two cents worth.
Psalm 127:1 Unless the LORD builds the house, the builders labor in vain.