My colleague told me to teach the child hold the pencil this way:
1. Take a coin. Have the child pinch the coin in his/her pinky and ring finger.
( you can use others suitable materials to replace coin, etc button,
tissue paper...)
2. While the child still pinching the coin in those two fingers, tell him to
hold the pencil in the remaining three fingers.
3. Markedly, the child will naturally hold the pencil in the right way as long
as the coin is still in his 4th and 5th fingers.