hello friend, glad you like my book.
As far as your motors go, you are correct. The white wires are in fact for the electric brake which is under the metal (or plastic) cap on the back of the motor. For testing, you can apply a 12v signal (polarity should not matter) to the white wires, and you should hear the solenoid click and release the brake from the motor shaft - now you will be able to power the other 2 wires (black/red) with a 24v signal to see the motors spin. For a permanent solution, I typically recommend removing the brakes from the motors so you don't have to worry about constantly powering the release solenoids while in use.
There is an example of how to do this in the book... but typically, you will remove the dust caps and then several bolts using an allen wrench until the only thing left on the back of the motor is the output shaft. Then you will be golden. As for a motor-controller, I would recommend the Sabertooth 2x25 (as the smallest option), but the 2x60 would be super.