I did this a while back. I used 3 toggles and a momentary switch.
According to the wiring diagram, there are 4 circuits, to go with the 3 "on" positions in the ignition (I = acc, II = power, III = start).
--The accessory circuit (green/white wire, for radio/etc) works in positions I and II.
--One power circuit (yellow, for... well, lots of stuff) works in positions II and III.
--The other power circuit (white wire, for windows/wipers/mirrors /etc) only works in position II.
--The starting circuit (white/red wire) only works in position III.
So for mine, I just put a separate switch in for each of those circuits:
Switch 1 = Accessories (radio, mostly)
Switch 2 = Starting power
Switch 3 = Other stuff, like windows and wipers
Button = start
Since the ignition cuts out both the accessory circuit and one of the power circuits in position III (starting), I usually just flip switch 2 then hit the button to start. I could probably leave the other two off if I felt like it, but usually turn them all on after starting. (Though once or twice my wife has been puzzled as to why the windows aren't working... turns out I forgot to turn switch 3 on.)
If I want to run the radio and nothing else (like at the drive-in), it's switch 1. And so on...
For the wiring, I put a large 5 position molex connector on the wires after cutting them away from the lock cylinder. Like this:
http://www.molex.com/cmc_upload/0/000/708/756/1625-5C-Rec_ISO.gif
Then I wired my switches into a matching connector, as if they were some sort of "module". I ended up binding the switches together into a block with electrical tape to make them easier to work with, and ended up leaving them that way. (I consider it temporary, but it holds together surprisingly well.)
For now, the "switch module" is sitting right on top of the steering column, and works great. I haven't decided where exactly to put them permanently yet. (Somewhere else for sure... they are pretty conspicuous there.) All I'll have to do is fab up an extension cable with the right molex connectors, route it, and then unplug/plugin the module in the new location.
Now, it'd probably be overkill to go out and get molex pins/housing/crimper/etc just for this, but I find them handy for lots of things, so I happened to have them already.
Looking at Chapman's 2-switch design to see which circuit he has on which switch, it looks like one switch has the ACC stuff, and both power circuits on the other switch. (Which is nice... my 3 switch version might duplicate the cylinder switch more closely, but is perhaps silly when you think about what it is doing and how it gets used.)
But I do think he has the description mixed up a bit...
If the first switch has the white & yellow wires, it would be ignition power, not ACC.
If the second switch has the green wire, it would be ACC power, not ignition.
Of course it doesn't really matter, it all works the same. But if you wanted to mount your switches in a particular order, it might save you 2 minutes worth of switching them back around.
I still need to fix the cylinder, though. It's starting to stick pretty bad. (I originally bypassed it because of an electrical issue, where power would remain on even with the key off and removed. Weird.)
On one of my other cars, it was possible to remove the cylinder itself from the casing (without any bashing or chiseling), pop all of the pins out of the lock, and put it back in. After that it was smooth as silk, with no sticking. Is something like that possible with this one, or would that even address the sticking? (I guess that'd depend on where the jamming in mechanism takes place.)