This is not a matter of power up or plot no jutsu... if you read the manga and watch the anime, you will realise that Tobi actually knew a lot of stuff because he had madara's memory. And all those times when he let Nagato (pain) lead akatsuki, did you all think he was just sleeping and eating... Nah!!! he was gathering info and getting zetsu to record all kinds of stuff for example; the technique of Tsuki no me he used in the Road to Ninja Movie... you could ask where he learnt it from, but it was Madara that came up with the hypothesis and Obito simply tested it... even the uchiha kinjutsu that he used to protect the statue before it turned to juubi was learnt either by practicing or learnt from Madara