From someone who has been there here is my recommendation:
1. Get the Bob Tait book...live it, learn it, breathe it...if you go through that book and can do all the practice exercises, you are halfway there
2. Use the Bob Tait practice exams...sit them in quiet (test) conditions...have all your materials there (the ones allowed for the test) and have a crack at finishing in the allotted time...AFT and Bob Tait use the same cyber (practice) exam format (I don't think AFT have ever done IREX but have always deferred to Bob Tait)...if you can knock a few of these over, you're pretty much set
The bottom line with IREX is really knowing the pubs (where to find things in the ERSA, CAR, CAO, etc) and being able to apply TO and FROM rules when trying to figure out where you are and where you are going.
If you are in NSW, I can recommend an EXCELLENT school at Camden which I used and between the points I made above and the additional tuition I did with them, I nailed it first time out of the box.
I'll offer this one final piece of advice...perhaps this is the most important one...you've got 3.5 hours for the test so don't go in there trying to nail it in less. Read the WHOLE question. Read it again. STOP. Figure out what they are asking (try to disregard the irrelevant info). THEN, and only then, look at the answers (ALL OF THEM). Pick the best answer. These tests DO aim to trip you up, so reading carefully the ENTIRE question and ALL the answers before selecting one is very important.
I wish you luck...PM me if you want the contact for the guy at Camden...he's worth every penny (its only ground school, so not all that expensive).
HP