This is a bit of a toughie! Commercial crew generally advertise in the yachting press and increasingly more in Trade-A-Boat. Private crew I suspect don't generally advertise in Oz because of the demography. We live in cities on the coast. We have very predictable winds along all sectors of the coast, and almost every boat which arrives from across the Pacific will ultimately sail north, then west following in each other's wake.
The trip along the east coat can be punctuated on an almost daily basis by dropping the hook at night in the lee of an island or behind a mainland cape or headland. Consequently, it is ideal for couples who wish to sail 'downhill'. For those who do require additional crew, the port cities and town, particularly as one moves north, are populated by a high number of backpackers, most of whom have 6 month visas, have a huge land to see, and who traditionally also move north and west from their point of arrival.
Then of course there is our natural good nature, love of a crowd (so long as there is a beer in the offing) and the knowledge that most of the best boozers are near yachts.
Considering these things, I think finding a crew is almost as easy as standing in a pub and shouting "WHO WANTS TO GO SAILING"...or posting a small note on the noticeboard at the local yacht club and laundrette.
I can't offer any suggestion other than that.
"if at first you don't succeed....Redefine success"!