I've found the best way to remove ball joints is a combination of a tie rod end puller and a hammer. Take the castle nut off, put it back on backwards (VERY IMPORTANT - keeps ball joint bolt from collapsing), put the tie rod puller on and tighten it down a bit - not enough to break it free, just to put some pressure on the joint. Then use the hammer on the knuckle. This method has worked really well for me.