Your XP analysis kit is a pack of blank cards. Four by six or 5×8 unlined cards are about right. Experiment a little, but you'll probably wind up wanting to use only one size card throughout your project. They're easier to handle in bulk if they're all the same size. And get lots—we use them for everything, and we like to tear them up.
You'll need a comfortable space where a couple of customers and a couple of programmers can sit at a table and work. Use your planning table or any other convenient spot. Customer and programmer sitting side by side, not across the table, works best.
Unwrap the cards. They're hard to use in the plastic wrap. And the unwrapping is the hardest part of the process. Whew, glad that's over.