To call Johann skeptical about improving his Windsight would be an understatement, as it apparently sounds to him like some of the more esoteric parts of the arts of the Pick of Grungni that he tried and failed to reach an understanding of. But either out of respect for you or gratitude for the company, he barely puts up a fight and allows you to drag him into the White Tower, and you don't protest at the pack following him - both because you doubt you'd be able to separate them without a lot of trouble, and because they'd work quite nicely as subjects for observation.
Magical senses are tricky things, right down to appropriately naming them. Current convention amongst the Colleges is 'Windsight', which is misleading on two levels as it isn't restricted to the eight Winds, nor does it always manifest as sight. In the recent past 'Magesight' was preferred, but one does not need to be a Mage to possess it - many people can perceive magic without any ability to manipulate it. Some more mystical types say 'Spirit-Sight', which might be the most correct of all if certain theories about the nature of magic and souls are correct. And in the common parlance it's 'Witchsight', which is just plain rude. Whatever name it goes by, the fact is that it's not a single sense at all, but a label applied to however a person perceives magic, and there's as many ways to perceive magic as there are people capable of doing so.
To you, Windsight is mostly sight, though Dhar has an accompanying smell and the Waaagh is more of a mingling of taste and sensation. The sense Johann describes to you is very different to conventional senses, and he haltingly does his best to explain a constant awareness of his surroundings, and eventually settles on describing it as being able to know where a fire is by the sensation of heat on your skin. To this sense, open air feels different enough to inert stone walls that he's still mostly able to make his way around, and various types of magical energies are sensed as a sort of once-removed emotion. But, naturally enough, it is various metals that his magical sense is most able to perceive, including the ability to discern alloys and roughly gauge purity at a touch. It does present something of a stumbling block for direct study, but you're still hopeful.
[Mathilde's teaching: Learning, 33+27+10(Windsage)+2(Library: Chamon)=72.]
[Johann's learning: Learning, 90+14+10(White Tower)-10(Inflexible Magic)=104.]
It goes a lot better than you expected. Your own magical sense manifests omnidirectionally, so after some trial and error you're able to find common ground and develop a good understanding of how he's perceiving the world. From there, you take him through some of the more basic meditative exercises of the Grey College, which is a lot better received when you tell him that absolute stillness is not required, nor is refraining from playing with his wolf-rats. Under your thoughtful gaze, he quickly and unknowingly hones his senses on the nimble and energetic creatures, and it's not long until there's no hesitation at all in his reaching out to rub ears, scratch shoulders, and tickle bellies.
From there, it's simply a matter of escalation, starting with simple sorting exercises and quickly moving on to more energetic pursuits, from throwing sticks for his wolf-rats to making his way carefully through the sprouting cabbage fields without crushing too much of the crop underfoot. Eventually you reach the point where you're throwing an ovular ball wrapped with iron wire back and forth, hindered to no small extent by the wolf-rats and their ability to jump higher than a man when they feel they're being left out of the game. By that point, Johann has regained his old confidence, and only the blindfold over his eyes indicates that he's not currently able to see.
