This. I always had the theory that Kurama's "interference" was why he had so much trouble mastering the Rasengan. With that out of the way I think he can do it himself. Just a theory.He was able to surpass both of his parents in term of chakra control said the kyuubi, while sending different chakra to everyone, matching their chakra pattern perfectly. I think that during the battle with Sasuke, he made a Rasengan without clones 2 times already, so there is that as well.
This could have been very much the case. Maybe most of his chakra was used to keep the kyuubi at Bay.This. I always had the theory that Kurama's "interference" was why he had so much trouble mastering the Rasengan. With that out of the way I think he can do it himself. Just a theory.