I read the article on NoStockUI as previously linked to when it was first published, and have used it several times since. Eventually, I needed to do the same thing on my laptop, which is still running Windows XP, and the command line instructions given in that article didn't work on a pre-Vista OS, and so I was forced to find an alternative. What I found was a freeware program called
Junction Link Magic. Not only does it work in XP as well as Vista or Win7, it also simplifies the process of creating symlinks if you don't feel comfortable with a command line.
So, basically what I do now is if I've got c:\WoW folder, I make a c:\WoW(Druid), and then copy all of the files but none of the folders inside the first folder to the second. Then use the program I linked above to create a directory junction from c:\WoW\Data to c:\WoW(Druid)\Data. At this point, the new WoW folder for your druid is still missing about 6 folders that the original has. That's OK! Just run WoW.exe from the druid folder, and log into your druid. It will create automatically all the rest of the folders with exactly what you need in them, including Interface and WTF folders. Then log out, add in whatever custom addon files you need, and you're golden. Just create a shortcut to that wow.exe, label it Druid, and use that to launch WoW whenever you are playing your druid.
That said... I've found it tremendously lightens the burden of attempting to learn multiple classes and multiple specs to keep as much of my interface the same across all my toons. It's more complex to figure out how to set it up, but is very much worth it to me. I mean this to the point where my mount button is the same for every character, every character that has an interuppt on a 10s cd is bound to the same key, class-specific buffs are all bound to the same key, etc. I really think that's the way to go.
Good luck, and let me know if there's anything else I can do to help.