JAB,
If the rating has expired by less than 3 months, the ATO can decide no " refresher" training is required, if the rating has expired by more than 3 months and less than 1 year then a minimum of 2 training sessions is required. The length of the session and "training alongside checking" is by arrangement depending on case by case but if the candidate is not operating that type or a similar variant then I would expect 2 full sessions minimum.