Don't use any US based text, DVD or online course. USA has approaches & procedures that aren't used in Oz, Oz has approaches & procedures that aren't used in the US. Oz is PANS-OPS based, US uses TERPS. Rules, regs & procedures are like chalk & cheese between the two.
It's not that hard to study without attending a course. That's how I did it using Dyson-Holland's texts for the (then) two exams. Admittedly that was nearly 25 years ago but NDBs haven't changed much and there are only so many rules.