What controller do you use?
If you use a Gamecube here's what to do.
Then quickly move the control stick to the upward position. Then move your thumb over the X button then quickly slide it down to the A button all while still holding the control stick up.
Hold the A button to charge it
Jump canceling, then canceling that jump? lolwut
Did P:M's programmers intend for it t' work like that?