Whether before or after its improvement, practicing the Flying Charm came with a certain threshold.
At the very least, one needed to have formed a concept of the soul, possess a certain degree of Magical Understanding, and have set foot on one's own Path of Magic before it was suitable to begin practicing the Flying Charm.
As for what the exact standards were, Vizet still needed to keep exploring.
While discussing how to lower the barrier of crossing "Animal Instinct" through the improved Polyjuice Potion, he took the opportunity to share his improved method of practicing the Flying Charm with Professor McGonagall and Professor Flitwick.
When he went to Greenhouse to help in the morning, he and Luna also shared the improved Flying Charm practice method while chatting with Sprout.
In fact, as long as he could get in touch with a professor, he would take the initiative to share this practice method.
Snape's situation was rather special. After class, Snape had his own "program" scheduled, making it difficult for him to spare time.
So Vizet could only make other plans, preparing to share the practice method with Snape when he attended Snape's private tutoring.
Vizet sharing the Flying Charm practice method also caused Moody some concern.
Moody had only retired. As for the rich combat experience of an Auror, he had not let go of a single bit of it.
So he was very clear on what kind of advantage one could establish in battle if one mastered the Flying Charm.
After more than a year of contact, he could be considered to understand Vizet's character fairly well. He knew Vizet was that kind of person, someone who had never been stingy about sharing knowledge.
The only advice he could offer was to make sure Vizet Always Stay Vigilant