Scottsdale FSDO
At the flight school where I worked, all our guys took their CFI with Scottsdale FSDO. You could count on AT LEAST a half day for the oral, sometimes more. Mine was 4 hours. (8-noon), and everyone thought I got off easy. The flight was very short however, I think it was 1.1 or 1.2, and it was extremely straightforward. But in the Phoenix area, the DE alternative is J. Bonesteel. I've never met her, I hear she really knows her stuff, and she's a great asset to the aviation community, but her CFI rides are truly brutal. I know a guy whose oral lasted all day. They did the flight the following day because they ran out of time.
Buzo, get ready to learn all of the things you thought you knew about flying. CFI'ing is a great experience. Enjoy it.