Hmm. Not sure what you mean exactly by a two post switch. Do you mean a regular make/break type of switch with two terminals?
If so, then you'd just hook the + coil terminal to one post and the - terminal to the other. When they're connected, the mag is defeated/grounded. Of course, you'd need the negative terminal of the coil grounded to something good too.
Lots of folks run the hot wire from the coil to the switch, but then just run the ground side of the switch to the chassis or something. The best ground is the other terminal of the coil. You have to run two wires to the coil instead of just one, but it really is the best way to go.
If you're referring to a different type of switch, let me know and we'll figure it out!
Spud