after 15 years or more of fishing the Hawkesbury, i can tell you i agree with the concept that it is great 1 day and hopeless the next. I have found coal and candle does produce some good fish at each end of it but you do need to be patient, try different baits and pray to the fishing gods.
Ken used to have some info on the best spots as he is a hawkesbury Fishing God but i am not sure if that section is still on this site.
I also ageree that since the pro's were kicked out of sydney harbour the fishing in pittwater has gone from bad to worse. That isnt going to change any time soon so you do have to go where their nets cant.
Good luck and dont despair, you can always get out the front of Lion and catch salmon at this time of the year and they are great fun to catch on silver lures.