These are the solenoids I use:
If you're considering tackling this project, I recommend using a different HighlyLiquid kit than the one mentioned in the article. John has come out with some newer ones that work a little more cleanly than the MSA-R.
You should check out the MD24: http://highlyliquid.com/kits/md24/
It's got 24 outputs, and can control servos directly for a quick and easy solution. You can also drive transistors with it for activating the solenoids.
Please feel free to ask me any questions as you get into it.