Any suggestions/methods for helping a young teen to improve his handwriting?

DS13 recently asked me how to improve his handwriting. He doesn't know how to write cursive and his handwriting is sloppy. I have complained in the past that it is barely borderline legible and have gone as far as to request an OT assessment in 2nd grade and in 4th grade as I was concerned with some form of dysgraphia although content-wise his writing is strong and quickly produced. DS13 was informally assessed both times. However, teachers are more skilled at deciphering bad handwriting and do not see a significant problem plus the OT assessed his handwriting issues to fall within acceptable parameters and clocked his writing speed at well above the minimum threshold. There is no functional impairment per se as he receives A/A+ on writing assignments, including handwritten ones so there is no basis for requesting help from school.

I think DS13 is sick of always having to dictate during group work in class, particularly as he often provides a majority of the content. He sees it as a handicap. The other kids are nice about it and volunteers to scribe and it has not affected his popularity/desirability as a group member so again no functional impairment as far as the school is concerned. From my perspective, I have seen how laborious and time-consuming it is when he has to copy essays neatly on applications when typing is specifically not permitted.

Anyhow, I am at a loss as this is something he should have fixed years ago but I could not have forced him. It seems to me that he has to learn to write neatly and then practice writing that way over and over again.

Any ideas?