The Multi-Pour is one of the best crowd-pleasers I know. Ironically, it is relatively easy to perform once you learn a few basic tips. Be sure to start small with just a couple tins/shots. As you get better, see how many you can do and have fun stacking the shots at different levels to create a more impressive display. BE CAREFUL to find your limit of how many you feel comfortable with - I usually max out around 11. Any more than 11 and I worry about the tins slipping apart while I'm pouring and breaking the whole display. Which is not good. Practice until you find your own comfort level.
ALSO, one of the best uses of this trick is to let the customer pour it. In a flair bar, when you've been entertaining guests and couples, it's not uncommon for a girl's boyfriend to get all Alpha male and eye you suspiciously. After all, you've been making his girlfriend squeal with excitement all night. The best way I've found to win him over is to set up the multi-pour (if you're doing five or less) and when it comes time to pour, tell him you need a break and that it's his turn. Make sure you set up everything right and that you walk him through how to pour. Show him how to grip the tins and make some noise while he's pouring - let everyone in the bar know that this guy kicks ass. You do the setup, he feels like a big shot. And if he doesn't tip you big by the end of the night, go home with his girlfriend.