I plumbed air into the coolant supply line after the ball valve and use the spare M code relays to wire in a solenoid valve. So when I want to use air, I close the ball valve so it doesn't back feed air into the coolant tank, and runs air through the turret like coolant normally would using M51/M61. Downside is, if you need to use coolant at the same time, its one or the other.