It is always a little bit harder to find a method (and media) for Dek Ai to learn things. It is also a little bit harder to ask him to hold a pen or pencil and scratch.
I just found that this one works quite well. Pencils on floor and he started to 'draw' a ball. I drew some stuffs and numbers, and there he started to recognize number 1 to 3.
We'll keep working on this, for sure :D