I do believe that typing unlocks the door.
In the meantime, write down what he says. Perhaps a dream journal, or a website forum of his favorite topic (TV show, game, book etc.) If he hates handwriting, then try Handwriting without tears for 2 minutes a day. If he hates composition, wait until the typing comes it. Also read "6+1 Writing Traits" books - very useful for figuring out what is involved in composition.
Limerics, jump rope rhymes, might catch on. Pay him to compose answering machine message songs?
typing opens many doors,
Trinity