PLEASE can anyone tell me how to do this. I have tried every gadget in the shops and I just end up in a sticky mess. My latest effort was with some plastic "concertina shaped" containers of different sizes - piped fresh cream ok but not buttercream. I notice on The Bake Off they all use those blue piping bags. I've tried them too but no luck, more mess! I don't understand how you fit the nozzles to those piping bags? Can anyone help?