I did this last year.
As SteveL said you cancel the registration; hand in the plates. The buyer will then have to contact VIC roads and apply for a temp registration permit, which is purchase by the day. The can be arranged by him at any time and he will have to state the needed days for journey. When filling for form, which they fax to him, he will have to state the current garage address and his intended destination, the vehicles VIN & engine number and both your details.
From here he will be pulled over about 20 times in the north mid NSW stretch of the hwy from having no plates however if all paper work is in order he'll be sweet.