NUNS3 Kamui Hack
So I discovered this accidentally, and I've gone on to use it repeatedly against opponents. It's an almost guaranteed way to fire off a successful Kamui about 7 seconds into the match.
Now if you've come across players like me, you'll notice that the first thing the opponent does is block. This is good.
First thing you want to do is put up Kakashi's Kunai Rain, next get Ready a Raiju Hashiri no Jutsu. What I've come to learn is that if an opponent blocks the Lightning Beast Running Technique, it literally takes a single Kunai to stun them. When the Jutsu is combined with the Kunai Rain, you're guaranteed a stun, and then you can either you use the stun time to recover chakra, or immediately use Kakashi's item to regain chakra and your opponent is wide open to take the full blast of his Kamui.
Enjoy trolling people my children.