rough roads at the best of times, with this rain .. who knows???
allow 4.5 -> 5 hrs (average speed 30 -> 40kmh) and take a chainsaw.
the extra time will allow "some" track clearing.
couple of ways to go:
Walhalla, Mt Useful, South Rd onto Jamieson-Licola rd, Jamieson, Howqua.
or
Aberfeldy, Matlock, Woods Point, Jamieson, Howqua.
take your luck on the day
, probably six of one and a half dozen of the other.
Have a good one ... stay the night and drive back the next day.
Stevo