Switch Positions:
Position 1 - Bridge
Position 2 - Bridge/Neck (hum-cancelling)
Position 3 - Neck

This diagram allows the neck P90 to see its desired 500k resistance while giving the bridge single coil its desired 250k tone pot. The bridge ONLY will be affected by the tone pot. This wiring schematic features a traditional 3-way blade, a treble bleed circuit, and the middle position is hum-cancelling.

NOTE:
Polarity (Measured to the strings)
Neck = North
Bridge = South