Crazy man, like assuming you're hitting it the way I'd be hitting it... they just come apart like magic. Northeast trucks, Michigan trucks, Arizona trucks.. all of them.
I don't want to insult you at all, I am like 99% sure you're doing it the right way based on your description but in the interest of trying to help - you're hitting it exactly like what's shown in this video (except upper ball joint... well, all cone seats work the same way) ??
When I'm junkyarding 90's mitsubishi front axle assemblies all I bring with for ball joints is a little framing hammer and I've never come home empty handed. Same trick took my Ram front end apart several times.
Oh, yeah and I wouldn't be using a dead blow... brass hammers are great for this or if you don't mind a little bit of cosmetic damage you can just wail on it with a steel hammer. You want to take that round cone shape and "ring it like a bell" , make it get all
warbly from the impact. That's what makes it let go!
Please wear eye and ear protection though, ANY time you're hitting anything with a hammer on a car!!