Wire the switch in to a reverse fed relay, powered by a momentary hold button.
Place the button underneath the shifter boot and mount with a bracket in a way to have it pressed in while in first, but released in 2nd or higher. Then, if you are in first, the button is depressed, which will kill power to the relay which feeds your setup.
once you shift out of 1st, in to 2nd or higher, the button is no longer depressed, the relay is energized, and your setup is powered. go WOT in 2nd and it automatically is spraying. no hands off the wheel, or the shifter.. tada.
