Did they change the Dire Maul North ghost ogres? Because they all have 1 HP and are immune to attacks so you can just sit there auto attacking for skillups and AFK. I've been away from the game a little bit so if it has been changed, I was unaware.
If they haven't then are found on the outskirts of the King Gordok area. The King and Chorush are in the middle platform, while the ghost ogres are on the perimeter walls surrounding the middle platform. Bring all the weapons you want to train and just auto attack. Of note, your weapons will still lose durability even though you aren't being hit and that you aren't doing any damage. I have 399/400 daggers on my druid because the dagger broke before I could get the last skillup.