Attacking is rhythm-based...You waggle, then wait a half-second and attack again, and keep up the rhythm...It takes a little time to get used to, particularly when in the heat of battle you just want to waggle as fast as you can... =)
Second, I never bothered with the Z button, as I felt it made things harder...Just do a quick motion left or right...Again, it's something that may seem difficult but is a cakewalk once you get the hang of it...