G'Day Ants,
I commute out that way (to Camp Rd, Broady) quite a lot in the past 6-7 months.
I've devised a route from the CBD on main roads that I think is as safe as any other way out there.
It does use Sydney Rd but only about 6k's of it and 4k of that is once it goes to triple lanes. It's not that bad these days as most heavy vehicle traffic uses the Ring Rd now.
As for bike paths I was told to avoid the Upfield Trial as it is helter-skelter & in really poor condition.
I have also tried Merri Creek but tbh it weaves so much that it adds 15-20mins for the equivalent travel distance.
Have not used the Western Ring Rd track but I have been told it is very good.
So I head out of Melb on Exhibition St, which turns into Rathdowne St until it ends.
Turn Left onto Park St then turn Right onto Lygon St which turns into Nicholson St & take it until it ends at Bell St
Turn right onto Bell St then next left onto Elizabeth St after you cross the bridge over the Merri Ck
Turn left onto Murray Rd then turn right onto Sydney Rd & just before you get to the Western Ring road you should be able to get across onto the Ring Rd bike path heading to Campbellfield.
Have a look at my path on Strava:
http://app.strava.com/rides/1051949 Hope it helps.