Be aware of terminology between the different regions. You may be surprised about just what qualification you get (and the privileges associated with it).
USA: CFI=Certificated Flight Instructor. Takes about 12 hours flight instruction + a flight test/checkride. Carries with it full authority & responsibility to teach - only in single engine aircraft - at all levels, send 1st & subsequent solo, and to operate entirely without supervision** of a more senior instructor.
**but your student pass rate is monitored by the FAA. Too many failures can result in the FAA questioning your CFI qualification.
USA: CFII: Teach Instrument Rating stuff. Same requirement(s) re FAA monitoring of pass rate etc.
USA: MEI: Teach in multi-engine aircraft. Same limitations as the other instructor ratings re responsibility & authority.
Oz: CFI = Chief Flying Instructor. You are *not* qualified for this position as a new instructor (you need a Grade 1 instructor rating). So, what are the various instructor ratings in Oz?***
Oz: Grade 3: Takes 50 hours flight training. Can instruct under the supervision of a Grade 1 instructor. May not send anyone solo until at least 100hrs instructing experience, and then after that only for subsequent solo ie never 1st solo in any sequence.
Oz: Gr 2: 250 hrs instructing + a flight test/checkride. Can now send people for a 1st solo. With more experience may do Flight Reviews.
Oz: Gr 1: 750 hours instructing + flight test/checkride. Can teach instrument rating stuff. May supervise junior instructors. Can be a Chief Flying Instructor for a non-instructor school + some other limitations about the level of school.
Oz: Multi Engine Training approval: A separate 'add-on endorsement to a Gr 3, 2 or 1 Instructor Rating.
***Note that the rules in Oz changed recently so some of what I've written is somewhat outdated. However the gist is still much the same. Oz used to prohibit an instructor exercising most of the instructor privileges outside the auspices of a licenced flying school. That's been relaxed, unlike the US where, once you're licenced, you have always been free to go forth & instruct if you can find a plane & some students. In short, in Oz you answered to the CFI of the flying school (who then answered to the regulatory authority) whereas in the US you were your own (chief) flying instructor and answered directly to the FAA for your results.
They are two very different systems! What's more, a qualification in one doesn't transfer to the other.