I forgot that the idle speed on the Revo is set with the idle stop screw. I removed my opti drive long ago, and I set my idle at the tx, using the throttle trim knob. To kill my engine, I just turn the knob down all the way. Much better than plugging the exhaust with your finger.
My normal idle is about half way on the knob, that way I can compensate for engine temp as it warms up, which makes it idle faster... Just dont hit reverse until your stopped !