Pretty simple, Gut the original wand and remove the controller, motor etc.

Grind a flat/key on the shaft of the BLDC motor to slip in to the vibrator connector.

Machine up a holder that allows the BLDC motor to fit in where the old motor came from

Wire the BLDC up to the ESC and the EXC to the arduino

Modify the Pot/Switch and connect that to the arduino

Flash the ardunio with some simple code and Happy Teeth Rattling.

In this one I had to tweak the speeds down and run the motor at about 1/4 of full speed, apparently there is such a thing as too much vibration.