Sutherland to Phillip island via dirt

Im heading to the Motogp in October. Im after a route that will take in as much dirt as possible. Leaving from the south of Sydney, Sutherland. Timeframe is about 3 days to get there. Years ago there was a dirt track through Yalwal to Nerriga but I believe this is now closed. The section from Braidwood to Cooma is straight forward. Any info would be much appreciated.