Jim WB8SIW has done an outstanding YouTube video on “How to Properly Adjust and Use a Vibroplex Bug.”
Direct link is: http://www.youtube.com/watch?v=qekmyx31Uxw
The Michigan Radio Manual Jim WB8SIW mentions is at: http://michigannet.org/_wsn/page2.html
The quick few pages on Vibroplex Set-Up extracted as a PDF are:
Vibroplex Key Adjustment by Jim WB8SIW
Very well done and recommended!