Problem with the tap out deal is it often does unkind things to the motor. Now, if all you're trying to do is save the pinion and have spare or upgrade motors, go for it, and use the vice to press the pinion on the new motor.

A pinion puller is strongly recommended, however. In actuality, if there is a local shop that does model railroading, what we call a pinion puller they call a drive wheel puller. Same tool.