Originally Posted by toly
Anatoly, we all understand that supination is important. But when you want someone to to be able to pronate, you don't tell them to intentionally supinate! You can give them an easier tip that enables them to accomplish this, but it has to be along the lines of what Power Player and Cheetah have already said, not just "supinate more."
So you have established that OP isn't able to pronate because he isn't supinating. But you might be pointing out a minor point in a bigger problem in technique.