If you have to do it gradually--learned incompetence* with your MS duties, followed by stopping all forms of participation.
*Drop the mic. Turn the volume up all the way 'by accident' when you do the sound. Put the magazines away in the wrong area when you do the literature counter. Ask questions that are so basic they will wonder if you are stupid or just not well read on your towerology.
Now comes the fun part. Start saying odd things with increasing intensity. Ask if they saw a flash of light during the wt study, or if they heard those whispers during the service mtg--let them start rumors that you're being bothered by demons.
Then just disappear...