Somebody correct me if I'm wrong, but I'm pretty sure taking a shotgun through your nose shouldn't make any difference as compared to through your mouth. The coke passage way you are talking about is the mucus membrain, and the reason coke is absorbed is because it is water soluble. THC isn't. Thus, inhaling through your nose shouldn't make a difference. However, there is the ongoing debate as to whether xanax is more potent by insufflation. It isn't water soluble, so perhaps there is another means of absorption their.
As for giving shotguns, taking a hit before you blow it is essential. It's amazing how few people know that. Then make sure you breath out hard. Get that blunt burning and knock them over.