"More that a nine-foot-three quack who wears a paper bag on his head isn't somebody people want using esoteric methods of healing on them."

Yes, believe it or not, Faust is actually very aware of how he looks and comes off. Not that that's particularly relevant here, considering how remarkably well Zidane is taking this. The good doctor will drop the pose and continue addressing the young man in a more serious and formal tone.

"To put it into simple terms, the method of healing I was trained in is a form of spiritual transfer - where I am from, it is common knowledge everybody has a soul, and that various parts of our physical and mental wellbeing are intimately connected to that. Without a soul, we are literally nothing more than lifeless husks, so it is in everybody's best interests to ensure one's soul is kept as healthy as possible."

It's at this point the formality is partially thrown back out the window as Faust's hands begin moving in a flurry of gesticulating motion, almost subconsciously providing real-time translations of his explanation into sign language as he does so.

"However, it turns out whereas good physical and mental health leads to good spiritual health, the system actually goes both ways. By transferring raw spiritual energy directly into another soul, it is possible to produce a restorative effect to both body and mind. Though I should mention that such a process is incredibly delicate, and can have a multitude of varying side-effects of an undesirable nature if performed by an untrained individual.
...fortunately for you, I've been doing this for over three decades! As your doctor, I can confidently say that your soul is in extremely safe hands, should you choose this method of healing!"

Faust shifts back into another dazzling, impressive pose, so as to inspire as much confidence in his abilities as possible!
And also to further withhold the fact this is literally the only option Zidane has, at the moment. Fingers crossed...!