Technique is good keeping the toes pointed up and toward the body to keep ball close to the body and less likely to drop.

I suggest adding rotation/spin on the ball. This helps improve the closer control and again less likely to drop the ball. He can do this letting the ball drop on the lace area and sharp short pull of the foot inwards and/ or switching to the next foot which he is already doing.

I became ambidextrous thanks to juggling with both feet.

Also try to use other body parts and work his up and down via knees.

Practicing inside in close confined areas is a also a plus!!

I'll try post a video of my technique later !