Take a fools advice (wearing my farming hat
) ... get a contractor to do the lot, or at least get a contractor to drive the (treated pine)
posts for you and put up the wire / ringlock mesh yourself.
Pilot hole drilled and then rammed, the posts will be much more solid than what you can ever get by digging or drilling and then backfilling, (even if you ram them well).
A good (home made) rammer is about a 1.8m length of 20 - 25mm waterpipe, weld / fix a short piece (about 60-70mm long) of about 40-50 mm pipe on end (or use gal pipe reducer fitting) and fill it (the ramming end) with lead or lead shot.
I inherited one that grandfather had and it sure beats for ease of use, the rammer knob on end of a crowbar.
Joe.
Joe.