In vic you don't need a RWC to sell a registered car. But to change registration ownership you do. The RWC can become the buyers problem this way.
I didn't think you would need to do more that sell it and write the buyer a recipt for it. You may need to ring/ go into RTA (vicroads over here) and tell tham that the car is no longer in your hands, but that is about it really. I think.