Ask him! I bet he has a lot of the critical insight about what works best for him.
(Maybe he's already expressing it?) And I also bet that asking him is the correct first step to integrating the insight he doesn't have.
And I bet the fine details matter.
"when Leonardo painted the portrait of Ginevra de Benci in
the National Gallery, he put a juniper bush behind her head.
In it he carefully painted each individual leaf. Many
painters might have thought, this is just something to put
in the background to frame her head. No one will look that
closely at it.
Not Leonardo. How hard he worked on part of a painting
didn't depend at all on how closely he expected anyone to
look at it. He was like Michael Jordan. Relentless.
Relentlessness wins because, in the aggregate, unseen
details become visible. When people walk by the portrait of
Ginevra de Benci, their attention is often immediately
arrested by it, even before they look at the label and
notice that it says Leonardo da Vinci. All those unseen
details combine to produce something that's just stunning,
like a thousand barely audible voices all singing in tune."
~ https://www.paulgraham.com/hp.html
We all experience levels of communication that go beyond sufficient or effective.
There's probably a zone of virtuosity that's hard to get to but invaluable if achieved where his way of communicating best is obviously neither defective nor deficient but uniquely, non-fungibly, performant and contributive. I feel unlocking unaccessed virtuosity is the key to achieving the truly apex outcomes we all want.
Kudos to you for striving to be inclusive!
EDIT check this out:
"Benefit: More opportunities for quiet voices
In many teams there are a combination of voices, some
quieter and some more assertive. Having this diversity on a
team is really beneficial, but can make it hard for everyone
to be heard. Quiet voices can find it harder to find a space
to interject their thoughts, or prefer to take time to think
about their response before communicating it, risking the
topic ending before the thought is shared.
Text communication doesn’t discriminate against this
difference in communication style. Everyone can share their
ideas at their own pace, and the reader never knows how long
it might have taken to put thoughts into words. There’s no
waiting for turns, and order is more often determined by who
is online when, and what time in their schedule they have
blocked out for messages."
~https://buffer.com/resources/asynchronous-meetings/