Asking your friend to ignore him until he gives up sounds like a good idea. I'm thinking it should probably be followed by her acknowledging him once he has "given up" - to send him the message that nice things happen to calm dogs.
Another thing, you may already be aware of this but just in case you aren't: How have you been reacting to his barking? Have you by any chance been raising your voice at him, shouting at him to shut up? Cos the thing is, when a dog barks and a human raises her voice at him, to his way of thinking the human is joining in, barking along. So if he barks and you respond by shouting at him, he thinks he's the leader of the pack and he's doing the right thing or else you wouldn't be barking too would you. So just in case that is what you have been doing, try not to do it. Doesn't mean you shouldn't be firm, just means: Don't "bark" ;-)