There are special tools for the job, but they often damage the threaded part of the ball joint. And can be a pain to get them where you need them.
Search for "Alltrade 648626" I am not sure which one would work, but with a good kit like that, you can usually get the job done.
The BFH is usually the best method. I dont know how you tried to hit it, so ill explain how I would do it.
You want to hit the knuckle, right next to where the joint goes through (from the side). Also get a pry-bar and pry them apart as you smack the crap out of the knuckle. It should come apart.
Good luck.