Here are several solutions
1. Let several days go by and then rehearse the proper use of the Guff Counter with your students ... just as described in "Teaching Challenging Elementary Students" ... then have a student, a "good" one, role play the proper response when someone keeps guffing ... the proper response is for your students to say nothing to the student, but keep their hands up in the "please stop" gesture ... if the guffing continues, then the students, with their hands still up don't even look at the student ... explain that it is responding to a guffing student that encourages more guff ... and then, make a mark on the positive side of your Scoreboard because students did such a good job in rehearsal ... repeat this rehearsal several times so that it is clear how everyone should respond to ongoing guff ... and so that the guffer knows what is waiting
2. Let several days go by and then use either the Bullseye Game or the new Agreement Bridge ... the latter is a new download on this site and the former is described in "Teaching Challenging Elementary Students"
3. If you are in elementary school, use the Card Practice System with the guffing student ... if you are in middle school/high school use Power Detention ... these are described in "Teaching Challenging Elementary Students" and in "Teaching Challenging Teens" respectively.
... keep us posted on the results!