You need to charge it up from a distance, when Jigglypuff starts flashing is when you release it. (Though, Make sure someone is in the way, so you can hit them)
Ok. Good luck with that, later.
Sometimes I actually also play as Jigglypuff, just for the lolz. ((Rollout is the only good K.O. move Jigglypuff has xD))
I accidentally deleted my personal record, So in Group Records it says: "Most used Character: Toon Link"
While in Brawl Records it says: "Favorite Character: Lucas"