I think this, like most things involving teaching children is, individual to each child. I never gave my son a lick of hitting instruction till around 10 or 11 when he started getting really bad bat drag. From the start he loaded, used his hips, had a decent swing all on his own. So I left him alone. My daughter on the other hand swung all arms. So I had to instruct her to use her hips then to load and so forth.
I also threw easy to both of them teaching them to catch. I used a dart like throwing motion. Neither of them throw like that and both have strong arms.
Every child learns differently and at different rates. There is no magic one size fits all teaching method for anything.