Kakashi can use Kamui on himself. He required a lot of experience since he isn't an Uchiha and doesn't have Senju DNA.
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Madara could use it immediately because he has been using MS/EMS for the longest time period (more than anyone else), so he could probably activate Obito's MS pretty easily. He must have also helped Obito train his kamui before he died.
And to those saying Madara can't use kamui because he is the ten tails jinchuuriki, that is also wrong. It was a mistranslation. In the official Viz translation Obito says the only thing he can't do while being a Juubi-jin is use kamui for intangibility (like going through things). He could probably still warp into the Kamui dimension.
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Hope that helped
ok. I understand just fine.thanks