I found different recipes for this. Would you need to coat the cake first w/buttercream icing prior to pouring the ganache over the cake? And how long does it take to cool once on the cake?
If you want a smooth cover, yes, it needs buttercream. the smoother the surface, the nicer the ganache will flow. It should only be warm, not hot, so cools in a few minutes.
It can be refrigerated, but it will lose some of its shine.