Got a torch? When I had to scrap stuff at my old job, removing the brazed-on bits was part of separating alloy from pure copper, so I'd just heat up the braze-on and give it a tap with a screwdriver or even better I've since learned is simply brushing it off. You have to keep the torch heat pointed at the braze on and away from the frame tubing (this should be obvious and if it wasn't I'd recommend not using torches)
In fact, if you have the braze-on pointed down you can usually just heat it up and it'll fall off... but the brush helps scrape off the alloy a bit. You can clean up the hot alloy with a dental pick or an old spoke too. The nice thing about this method is that you can be done in a couple of minutes assuming you have a workshop set up with a torch and bike stand.