You're the Man!
I actually figured it out after I posted asking you to post the instructions. I was going to do a write-up myself but you beat me to it. Don't worry though, this will help a lot of other people who are interested in this great feature.
One thing I noticed that contradicts your previous post. When the client loses connection I was able to reconnect without using the password and without going through the process of connecting them again.
If you want to disconnect the guest, select their MAC address from the Access Control list and click the '-' button. If you disconnect the client this way then the only way for them to re-connect is to go through the process again or give them the password to connect the regular way.
WINDOWS CLIENTS
First of all, this does not work as smoothly with Windows but I guess that's to be expected.
Some info about my Windows test environment. I tested this in Windows XP running on my MacBook Pro using Boot Camp. To take full advantage of the Atheros chipset in the MacBook Pro I also installed the drivers for the D-link DWA-645 wireless card that uses the same chipset.
When it comes to this wireless chipset, and probably others, Windows has the ability to take over control of the card or release control to the third party driver and connection interface. This turned out to be very important when it came to trying to connect to the base station as a guest.
When Windows has control of the card, there doesn't seem to be any way of connecting to the base station as a guest. I tried every way I could think of but it kept throwing up a dialogue box asking me to enter the wireless password.
When I had Windows relinquish control of the card to the D-link driver and used the D-link provided connection wizard I was able to connect as a guest but it wasn't as smooth as with the Mac.
The D-link connect wizard would still throw-up the password dialogue box but when I dismissed the dialogue box, Windows would connect to the base station as a guest.
If I tried using the PIN number method, no PIN number was displayed. If I tried the First Attempt method, AirPort Utility would not show that the guest client had connected. Further, the guest client is not listed in the Access Control list on the base station so you have no control over how long or when the guest can connect and you can't disconnect them without restarting the base station. I didn't bother testing the 24 hr. restriction.