Depends on how particular about cosmetics. You can go without any protective material.
I take the balls out. Fold the head down. Cinch it with a ratcheting nylon strap. Remove the legs. Dolly to the car. Turn the machine so the bottom is facing the vehicle and take it off the dolly when the machine is the right distance away that when you tip it over, the front of the machine will be resting on the tailgate of the vehicle. (I'm doing this with a RAV4, which is an SUV with a low tailgate).
I deadlift the other end while leaning towards the vehicle (and most of the weight is being held by the vehicle). Then just slide it in. (You could have a piece of cardboard in the bottom of the vehicle to get it to slide in easier).
I've never had a playfield glass break this way. I've never had the head damage the siderails. If there is an actual painted backglass involved, I'll wedge some padding between that and the playfield glass.
I don't secure the game in the car and it doesn't slide around enough to cause any damage. Of course, I'm careful about not braking too hard.
If you are very picky about nicks and scrapes to the outside of the cabinet, then you might want to put cardboard around the four corners, and use plastic wrap as suggested above. You might also want some method to secure the dolly so that it isn't banging around in the back next to the machine. Honestly for me, that's the most likely cause of damage once it's in the vehicle.