I'd just go down Healseville - Koo Wee Rup Rd until you hit the Sth Gippy - I've ridden it the other way a few times & it's not too bad. Despite being a major route, the SG has an enormously wide sealed shoulder so it's actually pretty safe. Still, I'd suggest turning off at Lang Lang & having some back road fun.
Continue past the crossroad in the middle of "town" & head towards Nyora. As you skirt Nyora, don't cross the railway into the heart of the township (unless you want to stop for supplies or just a squizz), instead continue towards Poowong (always loved that name when I was a kid
). A couple of km on, you can either take the turnoff towrds Loch, then from Loch climb to Poowong, or continue straight ahead and ... umm.... climb to Poowong.
Continue through Poowong, through a little locality called Ranceby, then when you hit the T-intersection at the end, turn right & drop into Korumburra. Turn left at the highway & look for the signs on the right - not too far along - for Kongwak, Wonthaggi & Inverloch.
The road undulates for a while, then near Kongwak splits to go for either Wonthaggi or Inverloch. Take your pick depending on whether you want to go directly for Inverloch or through 'Thaggi & around Cape Patterson. Either way it's a breathtaking view over the coastal plain & Bass Strait off the last ridge just before you plummet down the hill, then flattens out for the last few km into either town, moreso into Inverloch; the Wonthaggi route stays in the undulations pretty much all the way.