Here's my take on it: If you are actually engaged in a situation in which the defense of self/others would be appropriate, it's also appropriate to take more effective action than just showing the gun. I think that the exception identified above relates solely to the situation in which one has a good faith belief, based on objective fact, that he or another innocent third party is faced with the threat of an immediate (or "imminent") serious bodily injury (justifying the use of deadly force); and then realizes that he's mistaken, and then puts the gun away. His defense is sound, though he didn't find it necessary to actually shoot anyone. I tell folks in my seminar that you're allowed to change your mind - having decided that it's necessary to kill another human being, one might reasonably decide that it isn't necessary after all, and put the gun away.
I also tell folks that unless and until they've actually got a good reason to shoot another person dead'rn a doornail, they should not make any reference to the firearm at all; don't show it, don't touch it, and don't even think about it. It's for emergencies, only. Never, ever, try to use the presence of a gun to attempt to persuade anyone to back off. If you need to make them back off, because you have reason to think they're going to seriously hurt you, get the gun out and shoot 'em. Otherwise, you back off; ask them pretty please to leave you alone. I want you to be able to testify that you begged them most courteously to back off, and that they insisted in their threatening behavior which you quite reasonably took as a threat of an immediate serious bodily injury.
Don't rely on that self-defense exception to the brandishing statute unless you're in court on a charge of brandishing because you decided you didn't need to kill the bastard after having reasonably decided that you were going to have to do so.
