I have heard to just keep you hands on the top of the wheel, and when they ask for license and registration I say "Ok, my license is in my back pocket, and the registration is in the center console. I am getting the license out first." Then I move my hands off the steering wheel.
The trick with the other guy's thing is that he gets a reason to mention a cop friend. It's a conversation trick.
Situation 1: Cop walks up. You mention your cop friend. Trouble will ensue because you're obviously trying to say "I'm friends with policemen."
Situation 2: Cop walks up. Asks why you're doing obviously bizarre thing. Say it's because your cop friend asked you to so that police can know you're empty handed. You've now responded to a question and managed to mention that you're a friend with the police. He can't hold that against you because he's the one that asked.
The "bizarre" thing, he was referring to is holding your hands out the window. Not everyone does that typically; and one of the most important things you can do is to keep your hands where the officer can see them as they approach. It's like a "social cue" that tells them you are clued in. They might be a little more willing to let you go.
