I'm talking T-posts, about 22" deep x 1-5/8" diameter x 24". I use a horrible freight SDS MAX (NOTthe regular sds) hammer drill and a little bitty 3.5 horse B&S 2KW genset with handle/tires, about like dragging a push mower. Little pancake compressor and a long wand blower gets the dust out of the hole if it really needs it, usually not I just hammer the post down into the powder to the depth I want and move to the next one. Key is a cruciform-tip carbide masonry bit, 24" drilling length, about $200. Two-insert tips are no good for hard rock, but the cruciform point of good quality will easily drill granite, it's a single-jack on steroids. Takes me under two minutes to sink 22" in hard crystalline limestone. For the T-posts I'm concreting in place, I have a 2" x 24" bit and that loads up the drill pretty good, it gets hot and I keep an ice chest and trash bag handy for long runs, but it does fine.
For corner and line posts I use a 28-lb rock bar with a pyramid point and a tuna can. Au Jus ladle for clearing deeper than 3'. If not solid rock and not wet clay, an Eager Beaver drilling tool that has the boring head on a bar and a flex-drive coming up from the 4-wheeled powertrain cart works really well for holes up to 9" and six feet deep, if you don't have a tractor. It's like one of those two-man machines but with a lot more power and it won't twist your arms off or beat you to death because the torque arm takes all the load, all you have to do is push down to make it dig and pull up to clear the hole. I have a 743 Bobcat but rented the auger machine for some parts (or at least to get TO the rock more quickly!) because it's faster and will go anywhere you can drag it, including 40 degree, scree-covered slopes where the Bobcat won't go.
