Use good quality tyre levers such as the Park Tools type or the Soma stell cored type. Nick your partner's talc, and having deflated the tyre, press the beads of the tyre into the weel of the rim and sprinkle liberally with talc.
Now press one of the beads into the well of the rim opposite the valve and work around with your thumbs until about 12 to 18 inches of bead is sunk. If it keeps popping up, use cable ties to temporarily hold in place. Then use a tyre lever to lift a small section of tyre immediately to one side of the valve off the rim and lock the lver in place using its built in hook around a spoke. With another lever the other side of the valve, do the same. As this section of tyre comes off the rim, you should now have a continuous length of two or three inches off the wheel. Now go back to the bit you secured with cable ties earlier and working away from the ties, sink more bead. At some point you will probably feel the tension in the bead relax. You can then remove the rest of the tyre with fingers only.