It might actually be impossible.
When Dio drained blood from people in part 1, he was also infecting them with, or pumping some sort of essence into his victims. Basically flooding them with bacteria that puts them under his control. This control comes from resurrection , that puts them under Dio's control.
Dio is taking a much slower pace of taking over the world. The fleshbuds are like the flood of bacteria that creates zombies. However they're designed to be precise for controlling , this is key "living brains". They're parasites meant for the living. Dio did this because Jonathan showed him humans can overpower "transcended" beings. Dio is convinced that capable humans are above zombies. Hence the fleshbuds.
Due to Dio's death however, the fleshbuds have no owner. This makes them free to infect the living. Similar to zombie bacteria flooding in part 1. However this is happens on the "living form". Since the fleshbud is made of vampire cells, it fuses with the living cells of Okuyasu's giving him regeneration abilities and making him a hybrid of man and vamp. >Why Crazy Diamond won't work.
This means Okuyasu Dad is permanently changed on the physical level. He cannot be "fixed" because his form has changed too fundamentally. He is another being entirely now. A hybrid of living and vampire. >hamon
Again, the physical form has changed, Jonathan reversed the effects of "evil" in Brufords mind, but he was still a zombie and got burnt away by hamon. Also note that Zombies and Vampires burn up in the sun, whereas Okuyasu takes him out in the daylight, indicating that the weakness to hamon and the sun is not present in his farther. This probably because the farther is "alive" rather than a vampire. >Instagib
Killer queen would work, so would the hand. But I don't think Okuyasu wanted his Dad to die. Taking him out in public is a sign he isn't embarrassed by him and he wants a life with his dad, in contrast to his brother.