I have the 2 step wired thru a relay. The control circuit of the relay is a "latching relay" that is triggered by a momentary switch on the dash and released by a switch when the clutch pedal is released. The switch on the pedal does not release the 2 step until the pedal is all the way up. So when I am pre-staged, I hit the momentary switch to activate the 2 step. Then I can creep ahead to stage, without fully releasing the clutch pedal, so the pedal switch is not activated so the 2 step is still in play.
When I dump the clutch to launch, the pedal hits the switch and the latching relay is released, cancelling the 2 step until the momentary switch is pressed again while I am pre-staged on the next pass.

I like it because I don't have to think about it at launch, I don't have to involve my hand in the launch. Other than arming while pre-staged, it is all automatic.

A latching relay is no different than any other relay, it is only wired different.




the hot goes to a normally closed switch on the clutch pedal, that is opened when the pedal is fully released.