The crossfire uses a low power Reed relay to close the contact for the torch. Mine was a OMR-M-105H Reed relay. This could be different on your machine. From what I remember the relay was only good for 25ma or so at 5 volts. 12 volts was half of that.
If you want to put a solenoid on the machine you might need an additional relay for the solenoid. Someone on the forum has already put a marker attachment on the crossfire.