Treat it like the game it is and play slower than he does.
If they have TVs, watch TV instead of him shooting. Then glance when he shoots to make sure he doesn't foul, then watch tv again. Wait to shoot until he tells you it's your turn. Then act surprised and if you're playing 8-ball ask him which group you are
He'll quit doing it straightaway.
Celebrate his lucky rolls with him. Seriously. "Man, that was a sweet roll, you should have no trouble running out from here." (apply pressure)
And then when he doesn't: "Man, I thought you had that." (negative reinforcement)
And then when he does: "Yep, just like I thought." (diminish his accomplishment)
And then when you get a lucky roll: (Every single time) "I guess it's just my lucky night." (give him a reason to lose... He'll already be running the tape in his head "He got lucky to beat me"... once you give them an excuse to lose, they can't win)
Make sure you say all of these things with a smile and no matter what he says or does, keep smiling. Shake his hand at the end, even if he doesn't want to. Win or lose tell him "great shooting." That'll really piss him off.
If you do all of these, I bet you never lose to him again.
Seriously, if he has to play slow to beat you, you have the nuts. The triple nuts. Everybody knows it but you.
~rc