OK, so I made my first batch of Bunnywoman's BC today. Very pleased with the results. I had to make the icing this morning in order to do a FBC transfer. I will not be icing my cake until later. Will I need to re-beat the icing before frosting my cake? Also, is this a crusting BC?

Yes, it does crust. How long it sits determines whether you need to mix it again. You will most likely just have to give it a quick stir with a spoon or spatula before using it but not have to beat it with a mixer again.