Yes, there has to be a "trick" to using a forced reset or bump stock. If you simply held the trigger back and the firearm fired rapidly, by definition that would be a machinegun.
The definition of a machine gun is it fires more than one shot for a single function of the trigger. Pulling back on a trigger that then moves forward again until your finger again pulls it is more than one function of the trigger. Each time the trigger is pulled to it's release point, a single round fires. it then moves forward to reset, then has to move rearward again to fire. Note the definition refers only to the trigger's motions, not the shooters.