I need a little help please.  I am making a Tennis Ball cake with the Wilton ball pan.  I would like to cover it with Ganache to get a nice round (and firm) shape.  However, I have seen that the better looking tennis ball cakes are piped with a star tip using buttercream...Can I pipe buttercream onto ganache and will it hold?

TIA

If you're going to use the star tip, I wouldn't think you'd need to make sure it's smooth underneath.  The icing from the stars will cover any flaws there may be.