If kakashi could do the rasengan without any training (that I know about) by coping with sharingan (probably) can other sharingan users do the same? :dunno:
This^Let me explain...
Rasengan requires extreme chakra control, shown when Naruto had difficulties and shown by the power it has. If you think about it, Rasengan is just a ball of chakra, but the fact that it's so well compressed and ''spins'' makes it so powerful.
Think of how a Katon requires the user to transform his chakra into fire and is nowhere near the lethality of Rasengan.
Now, let's get back to Kakashi. He has some of the best chakra control in the manga, because he has/had average chakra reserves, meaning he had to make the most of each jutsu.
Looking at Raikiri, we can see Kakashi is used to both shape and nature transformation, which does indeed mean he can use Rasengan, which he either learned from Minato or copied from Jiraiya or Naruto.
However, unless other Uchihas show extreme chakra control they can't use it. It's not an easy jutsu to learn.
tell them what they don't know plsKakashi learned rasengan before he got the sharingan. It was said that kakashi developed the chidori because he was not able to mix rasengan with lightning. Kakashi created this jutsu before he even got the sharingan so he must have already known rasengan.