I've modified three switches to work in auto so far. IMHO its not worth the amount of work it takes to modify.
You need a donor switch (most any Toyota auto down switch will work, I've used a Camry switch, a Corrolla switch, and a 4Runner switch).
Pen and paper for wire notes/schematic
You have to carefully disassemble the donor switch without damaging it. Desolder the wires from the connectors, note the wire color pattern and connector schematic. Remove the switch (keep track of the springs inside). Repeat these steps on the switch you will be modifying.
When resoldering the wires be careful of too much heat warping the plastic casing or causing other damage.
So far each switch I've disassembled has had a different wire color code and different connector pattern. But the vehicle wireing color codes have all been similar.
The switchs have been slightly different internally also, some have small metal springs inside and some have a plastic catch/spring.
It takes about 2.5 hours to modify each switch, they're plastic so you can easily break the catches when disassembling and reassembling. I had to use contact cement to reassemble one, and another I had to file some plastic off the side of the case to make it fit right after soldering heat made it warp.