If your plug fit originally, then a fiddle tuning key will work excellently, but perhaps you did like I did on one of my horms and cut the tip off to short, thus causing the pour spout to open directly into the main cavity with very little channel. Because it flairs out less than a 1/2 inch into the spout, there's not enough channel in my horn to grip a plug, so basically, I'm screwed. I hope that's not your case, as I ain't quite got that one figured out yet ::