How does one copy Susanoo in the first place...? I mean there aren't exactly any hand signs, it just comes out of nowhere. Kinda weird tbh. Also @ confucius, perhaps it was implying that you just had to master the unique abilities of said person's eyes first, since Kakashi knows how to use Kamui effectively, as Kamui is the unique power those eyes utilize, he should be able to conjure up a Susanoo, by that logic. Also by that logic you don't have to have amaterasu and tsukuyomi, as those were probably unique to Itachi's eyes, Sasuke's also because he's Itachi's brother, regarding the use of amaterasu. I mean, really, we haven't seen Madara use amaterasu/tsukuyomi, further supporting this thesis. Same for Shisui.