I have a nice post digger tool but my dad claims its cheaper and much easier to use metal bars. He has been using 3" (?) metal poles and pounding the ends into a sharp flat surface and then hammering them into the ground.
I have also seen pneumatic fence post drivers (such as http://www.rohrermfg.com/) which would make this work easy with t-bars.
In either case I would need to go 3' deep at least and I want to extend my existing fence, as well as support it (the previous owners did a terrible job and dug only a foot and a half down)
Is there any advantage to using wooden posts with concrete over the other methods?