Scuba Steve
Smash Ace
Meh, the best way to get L-cancelling down is to just do it while you play. If you do it in training mode, you won't get used to L-cancelling against shields and enemies as quickly, because the timing is different.It sounds boring (because it is) but the best thing you can do is go into training mode and do it over and over until you can do it over and over- without messing up.
Also tip for teching: If you press the button too early, just hold it down. Lots of times it will do it anyway.