Greetings,
Using the speed control facilities original to the device would likely be simplest, as they’ve already been designed to accommodate the motor in question.
Assuming you have a brushed DC motor rather than a BLDC or a universal or something else, a common DPDT switch can be a straightforward means of direction control as described here and in may places elsewhere. Not all motors are conveniently reversible however, and taking the time to understand exactly what sort of motor you have would be useful.