Teaching a Pre-Schooler to Write is a Challenge

Mikael, Knows and familiar with the letters, Numbers,and shapes. Now he's three years old i started him to practice writing his name.At first he was using colors and he loves it but when i gave him the pencil,All his attention was focus on the pencil because it's hard and it has eraser.He did'nt want to draw or write. At first, i let him do whatever he wanted.Lately,I force him to drew a line,I showed him how to do it.I noticed it's very hard for him to hold the pencil,He can't hold it hard.I'm struggling how can i teach him how handle it,It's a challenge for me also because he is left handed.He cannot hold it until now.I read some article that "Experts recommend pinching the pencil between the thumb and index finger and resting it on the side of the middle finger, but it's okay if your child holds the pencil with all three fingers."Some kids are still learning to hold down a piece of paper with one hand while writing with the other. 
I need more patient,and I think I should do some muscles exercise for him.Good thing is he's trying and i will make teach him just like we're playing sometimes i forced him it looked like for him it's a chore to finish.I need more Ideas on how to teach like him to write.By next year he'l go to school.I'm his first teacher,I will help him before he enroll. 
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