Don't erase his writing only because of they're not pretty. Since K1 children can't contral their wrist and fingers well, so it's natural their writing is untidy . Your son dosen't like writing because he finds writing can't give him a sense of achievment. You always tell him this is not good, you're so slow . Try another approach, only correct the writing which is wrong not those not pretty and more encouragemrnt not scolding.
For my son I just tell him his writing is not bad but this ans that is not good anf dosen't look like the teacher's sample. If he really have difficulty in specific words I will hold his hand and show him how to write foe a few time. For sequence of strokes I will tell him before he write rather than erase it after he write.
actually I seldom hold his hand but sometimes it let him know you understand his difficulty and mummy will help you. But after 1 or 2 times you, I'll ask him to write it by himself and tell him where to pay attention like 中字個口要扁D,直要好長係正中間。And remind him every time until he catches the idea.
My son is K3, but still draw character not write.I need to remind him 寫字唔係畫字要跟筆順,but he still op. a fast way to draw the lines than write. I think K1 is still very young and you have to be patient, later you will see he has a great improvement.