so, what I think you are wanting to do is have a normal plastic extruder AND the conductive paste extruder. Correct? Regardless, we need more information, such as board type and firmware. It will not be that hard to do, just set up as a secondary extruder with no heater or thermistor (I think). You could look into people who have done chocolate extruders as it is almost identical mechanically.
If you need some help, or don't understand what I just said, feel free to send me a PM anytime
Printer: Prusa i3, 2 E3D v6 Hotends, Arduino + RAMPS 1.4 with a Bypassed 5V Regulator, 400w Insignia ATX PSU, Custom Designed Bowden Extruders