I have a guitar with some sympathetic vibration coming from the truss rod. This guitar has the LMII double action truss rod which is wrapped with heat-shrink tubing, but nothing else was put in the channel to prevent buzzing (oops - forgot that step). My thought is to pour something into the slot through the headstock opening. Something that flows easily but will eventually harden just a bit or turn tacky - enough to stop the buzz. I'm just not sure what that would be. Any thoughts? Any better ideas on how to deal with this issue?