Well,… yes…it is kind of inefficient. That is, to settle a debate that is raging on a particular issue, a world wide council of bishops must be called, they all have to come to the location at great expense, and argue and hash it out together. In the past, I understand that they even had brawls and fist fights. But, in the end, the Holy Spirit made sure the councils came to the correct decision about the debate. So, as I understand “negative guarantee,” the Holy Spirit doesn’t simply tell, or reveal to the council what’s what, but keeps them from making the wrong decision! In whatever way you can imagine that may work. The term “guide” I guess you could use, in a loose sense, but it has too much of a positive connotation.
Yes, this is an inefficient process! But, it keeps important decisions from being made too hastily. Even so, perhaps that is why the 1st Vatican Council confirmed the old tradition that the pope can speak infallibly as well. If a decision on a matter is needed quickly, the pope can speak ex cathedra, without the cumbersome and expensive process of a council.
Human wisdom? Right again. Using their wisdom, humans ponder on the mystery of God. Some to wrong conclusions such as Arius, and some to right conclusions, such as Anathasius. At the Council of Nicea, the Holy Spirit made sure the Arians did not prevail. (Note that the divinity of Christ was not a new idea, but an old one. The council did not come up with a novel teaching, but confirmed the old, and rejected the new teaching of Arius. Infallibly.)