Hi Geoff
The way I understand it Flightwatch provides inflight met information, information on restricted area activity etc on request from you as the Pic. They're really providing information that you couldent obtain on your preflight and or updating information for you. Well thats what I've used them for in the past anyway.
Flight Following is a ongoing radar information service available in E and G class airspace which includes us in G class but below 5000 you would probably loose coverage very quickly assuming youre identified at all. At 5000ft coverage is lost before Maryborough, at 10 000ft you'd have coverage all the way from Adelaide to Cains coastal, I think.
The primary purpose of flight following unlike flight watch, is to provide information on conflicting traffic, and to help you avoid Class C and D airspace and restricted areas. So it does not mean if you have flight following you have automatic clearance through C and D airspace, but you will be advised if you get too close.
As far as Frequency"s are concerned I've used Brisbane Centre frequency 129.0 and the radio call would be as follows;
Brisbane Centre jabiru ....... request flight following
If it's available the responce;
Jabiru..... go ahead
Jabiru...... 10 miles west of Maroochy climbing through 4500 for 5500ft on a flight from Caboolture to Bundaberg
ATC will allocate a squark code
Set it in the transponder hit enter id
ATC will advise they have you identified and you're on youre way.
If you change frequencies to say a CTAF like Harvybay without advising ATC flightfollowing will be terminated. At 5500ft you overfly the CTAF outside of their airspace and you'll be notified by ATC of conflicting traffic anyway. Having said that the onous is still on you to maintain a good lookout at all times. Any level changes must be reported to ATC as well.
You can cancel at any time and if ATC can no longer track you or you leave the controller's area they will notify you with Radar service is terminated. When they do you can request hand-off to the centre you're entering and ATC will ask the next controller to continue your service and instruct you to change frequency.
I think Airservices must have something on their site that will probably explain it better. I got the info off a mailed handout about 2 years ago.
As far as heights are concerned 5500ft and above enables you to overfly most CTAF's and maintain radar coverage in order to utilise flightfollowing.
Geoff please verify my ramblings I"m not real cluee when it comes to airspace and would hate to give you a bad steer. I just feel any contact with ATC is good contact and when you know they have you identified and you have coms established with them the entire flight seems safer and more professional.
Regards Greg A