This is a beautiful walk, very lush and green, along gently sloping firetrail. If you would like to do it as a car shuffle, here is the the place on Hue Hue Road to leave a car: Google Maps Link. Note, dogs are only permitted on the Firetrails in Mt Allison.
Start, Dicksons Road: -33.22039754388292, 151.38975620269778 Google Maps Link
Turn right onto Parkridge Fire Trail: -33.22172589524017, 151.3978457450867 Google Maps Link
Hooray, you have reached The Top of Mt Alison, head back down the hill, turning left at the picnic area: -33.233123756785695, 151.40125751495364 Google Maps Link
Keep left on Francis Byrnes fire trail, keep left when it continues to Hue Hue Rd: -33.23758377539121, 151.39765262603763 Google Maps Link
You've reached Hue Hue Rd: -33.23962974402257, 151.40130043029788 Google Maps Link