Naruto Chapter 420

[Abdula]

@Tyreal: While you do have a point, you seem to be forgetting that the only thing the rasengan was strong enough to do when he made it himself with his two hands, was strip the bark off trees. Hence it being labeled incomplete. Look here and here. As for Naruto not needing the clones once the molding is complete, I think it was already mentioned that once the technique is created its self sustaining.

Why Naruto needs the clones is explained right here. Naruto knows exactly what he has to do he just can't do it properly because he sucks at chakra control so he needs the clones to help him. It has nothing to do with concentrating on his opponent, he releases the chakra and the clone takes care of the rotation and compression.

Actually i don't think manipulation has anything to do with it, all you have to do is disrupt the control your opponent has over your chakra by using your own. Remember the example jiraya gave naruto, he had to stop the flow of chakra on his feet and then quickly resume it at full force, that doesn't have anything to do with manipulation, just control.

I already took care of explaining the need for clones to use rasengan. Anyway I think you're right. It probably is just chakra control. Manipulation is probably limited to just changing your chakra's shape or nature and everything else is control.