It depends on whether you have basic, intermediate, or advanced controls on. I'd suggest to use advanced right off the bat so you get used to it quicker, you can't get the full use of offensive moves from the other two.
I have 2K3 for PS2, but assuming it's the same with just different buttons because of the diffeent GC controller obviously...
On basic controls, you press A to pass and you hold A to flip pass. Same thing for intermediate, and for advanced you press A to pass, and hold L and press A to flip pass.
And I'm not exactly sure how it works on GC, but the modifier either means it's the button you have to hold in conjuction with pressing another button to do the double function (example- A is pass and holding modifier + A is flip pass), if that's not right then it's just a button you press to change strategies, from like crash the net - to - positional. I can't remember exactly.
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