To trigger the servos I used a large N.O momentary switch. To hold the switch and provide a handle I used the housing on a regular ballpoint pen. Removing the end cap and ink cartridge inside the pen I fed the wires through and connected the switch, the other end was wired to the battery and racetrack. I decided to encase my trigger cord in some scrap paracord.
After all the wiring is complete tuck any slack wires behind the battery holder, then cable tie the battery holder in place. Then, test out your circuit by depressing the momentary switch, all the servo should activate at once.