Naruto can use one of his toad summons to fill their belly with that oil from frog mounts and simply wash obito with it and poof obito Is now a stone toad
he will slip through it and the best plan to kill him is to make kakashi use kamui and naruto will go in the dimension. kakashi will fight him while naruto will wait for obito to use kamui so he can have a chance of punching him.