Thanks for the link. I think that the key is soaking the soil a bit. Part of my pasture has been irrigated a bit, and the posts in that area went in quite easily. The moles have made it easier too, but I don't know what that says about the stability of the posts. I'm only keeping in Alpacas, sheep, and a Great Pyrennes that won't jump on the fencing, so it probably won't matter much.
I tried pushing some in with the bucket and with the hill adding to the mix, it just wasn't going to work so it got done the hard way. There watered areas were so easy that it wouldn't really be worth using the tractor except to haul the T posts, plumb bob, and assorted equip around.
Thanks for the replies!