Keep the flame on the stop itself, avoiding the stay as much as possible. When the braze under the stop melts, knock the stop off the stay. While the braze is still liquid, use a wire brush to brush the bulk of it off the stay and you'll have minimal clean up afterward.

N.B. Air/propane is unlikely to be hot enough to melt the braze. If you don't have a fuel/oxygen setup, use the saw and file method to remove the stop.