I'll ask the silly question first ... why the long way ... presume you want to triple your ks for training or some such, with a bit of hill-fest thrown in
more practical comments.
You likely know this ... but from your start point ... ride through hawthorne canal and dog poo park ... aiming for the bay run ... past La Montage ... and heading to iron cove bridge ... nicer ride all bike path. (alternatively if climbing is what you want ... then lilyfield road ... along mary to the pool and onto the bay run at the rowing club)
After the bridge, its all foot path ... or ... take renwick street ... should be less traffic ... until lyons rd ... from there is foot path until past hunters hill (not sure what happens with the interchange around there I think a bit of street hoping).
Not sure what happens then ... not sure I'd want to ride up burns bay road in peak hour ... but the right hand foot path is prolly more continuous ... although narrow especially if there are pedestrians.
Where you turn off to Penrose ... I'd prolly keep going to Epping Road via centennial... and then take the cycleway which I think takes you all the way to the bridge (sorry I haven't ridden all of this cycleway).
If your aim is to annoy all those happy people in cars heading to work ... then that Penrose turn off is prolly on the money ... hilly, and two lanes ... with one lane sections
*edit: just noticed manly vale on your location ...
Just incase you didn't know ... the quick commute from your start point is
- head to lilyfield road ... I'd go all the way down flood, then darley, up the hill to lilyfield road (you'll see bicycle garage).
- follow lilyfield road to victoria rd ... take the pedestrian overpass ... then cross Anzac bridge ... past channel Ten ... then Pyrmont bridge ... follow the cattle to King street ... up king to Elizabeth and your pretty much there.