From what I can tell, SS does it with A, A, Z (hold). You can usually tell someone did that by seeing their light shield briefly pop-up if not done perfectly. This is what I use.
You can do triple A with precise timing, from what I hear.
Having personally asked Darkrain he says, "A, Z, A, Z." That is not a typo. I said "what. 4?" And he said "Yup." He gentlemans to knees so fast too...
edit: Just a thought... You can buffer jump outta shield with the C-stick. Did you know you can short hop and aerial out of shield asap with just the C-stick?