The hardest part about binding Airtronics is holding the receiver button while powering up... I cut off all of my on/off switches, so I have to plug in the battery while keeping my pinky on the button.
Takes about 3 seconds.

I have six+ cars & four drivers/transmitters...
Do your self the favor & figure out what the center point difference from the M11x & the MX3x. There may be none, but the MX3fg & the MXsports are not the same...
Also make every ESC/Transmitter/Model mode center point the same. Steering being messed up isn't horible, but if the car takes off look out.

My kids swap cars from time to time & it is quick to change model & re-bind.
I don't let the kids use my transmitter too often.

Traxxas has auto model memory now, but I wouldn't recomend them to any one.