A manual boost controller and an electric boost control solenoid are two totally different things.
The manual boost controller is operated by the pressure of the intake manifold actuating the valve against the force of a spring. The boost pressure is set by adjusting the spring tension against the valve.
A boost control solenoid is just an electrically operated proportional valve. The more power you send to the valve the farther it opens. In order to control the valve you’ll need a sensor to read the manifold pressure and then a circuit or microcontroller to determine if the boost valve needs to be opened and by how much from the sensor readings.
If you just hooked up a potentiometer to it, the valve would end up being open proportionally to the amount of power sent to it. If the valve is constantly open at all, you won’t be able to build pressure.