I don't know which part you are refering to. I used a 5lb sledge to get the old balljoint out of the spindle, I used the tool from AutoZone and a 900ft-lb impact to get the new one in.
I don't recall running into trouble when getting the balljoint out of the control arm but if/when I do normally I soak it with nonflammable liquid wrench, then heat it with a torch (mapp or oxy/acty). I try to use this as a last resort though as heating your control arm takes some strength away from it. I've had many occasions on getting joints out where even a 5lb hammer didn't help. So it was a mix of binding the pickle fork with a floor jack, heating the joint with a torch, use liquid wrench or pb blaster, and beat it with a 5lb sledge. I haven't found a joint this method hasn't worked on so far, occasionally I've had tierods glowing red before they decided to give in though.
If this helps
here is how I did it.