I pipe dams with my buttercream, but what do you do when it's ganache? Can you just beat a small amount of the ganche to make it thicker to pipe a dam then add the filling?
Ganache can be piped without whipping it. I use Chef Taz's recipe from this site (love it!) and chill for about an hour. It's plenty thick for piping then and would work for a dam, I think.