I used this
[CWM][OTA][EL29->FF18] Rooted FF18 OTA update (patches your existing stock EL29 ROM) - xda-developers which is stock and has two version FF18+root or FF18+root+cwm. The catch is you had to be pretty much stock with just autoroot and cwm already. If you want the ODIN stock root then you can try this one
http://forum.xda-developers.com/showthread.php?t=1721229 as well. The first link was easy because I was able to download the patched zip to my SD card and reboot into the custom recovery and apply zip from SD.