If I were you, I'd definitely fly non-rev easily to HNL, then ID90 on Qantas to Melbourne. Not sure whether or not they fly to MEL diresct from there. Obtaining an ID90 is easy. If originating in ATL, the easiest way to do it is: going to the international check-in desk in the E concourse. Simply ask an agent for an ID90 on Qantas out of HNL, tell her what flight you want, and she/he will then ask you for your credit card and that's it. She will then hand you your itinerary and tell you how much it was. I have done this when non-revving to JNB on DL and then SA to CPT.