The genjutsu essentially works as the C-ranked earth jutsu, World shaking. This technique works by, affecting the inner ear and equilibrium. What many won't understand and will mistake for this technique for is a typical visual jutsu. This technique isn't a visual genjutsu. Visual genjutsu creates images through affected visual stimulus/affecting the sense of vision. This technique affects the equilibrium through the inner ear and by result makes the person's the people's vision is affected. However in the case of Sharingan genjutsu, this technique is not a technique that cannot be seen through by Sharingan based genjutsu since it is not a visual technique. Even MS wouldn't be able to passively break through the "see through" method.
Secondly, this technique is one of those "gotta get out of it through metagame" sorta jutsu since this technique shouldn't be distinguishable from either a) an earth technique (more specifically the Earth Release: World Shaking) or b) an ordinary sound based ninjutsu technique that affects the equilibrium.
Thirdly, thirdly is a word (just found that out as I was typing this) and a shinobi should not be balanced enough either in percieved equilibrium or actual reality to conjure seals to cast Kai or any other technique really.
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Downside is the metagame to this technique. What I mean is, this technique only becomes more vigorous when the user tries to stabilize themself. While this is a standard occurance given a disordered equilibrium, people read this technique and will thing "Okay I won't fight this, I'll go with it." It's not really metagame, rather it's study of the jutsu. In fact I doubt most people would think of the simple method I used to render this technique without metagame and, which would allow me to fight with a fair amount of lucidity. Here's a hint, this technique makes you stumble like the 'Drunk' if there were, say a certain taijutsu style that utilizes the movements of a drunk off balance such as this technique indicates, then they would need only to move in said style of technique to, for lack of a better phrase, stabilize themselves without stabilizing themselves. If you catch my drift, this is one method to which a shinobi can fight (mainly defend/avoid the follow up justu cast after this one, or if you are indeed close enough, fight a taijutsu) while under this illusion. Or a shinobi can fault the movements to where he can momentarily cast a seal and cast Kai (if he can decipher the genjutsu that is).
As to your last point, how I would go about it, well i sorta answered that.