6th grader, new to CM narration

I need some ideas on how to transition my 6th grader into narration and how to use it to help his writing abilities. This has been an area of great struggle for us.
We have used Primary Language Lessons when we used MFW curriculum for two years, but he struggled immensely when we tried to transition to Writing Strands (MFW recommendation for composition in 4th grade.) After that he used Essentials in Writing which helped him with the basics of parts of speech, putting together a paragraph, etc. At that point (end of 4th/beginning of 5th) he didn’t even know how to compose a full paragraph, much less write a full page on a subject.
For the last year he has worked through Easy Peasy (allinonehomeschool.com) which we used for 1 1/2 years because of our financial situation. He very much excelled using that, but I’m really desiring to switch us to a full CM approach, using literature, narration, etc.
As I am transitioning to SCM, I need a realistic game plan to get my oldest to a place where he is truly learning how to write and compose. He narrates to me orally, and though I’m new to narration, I do believe he’s doing a good job at it.  I have had him write a few narrations from his history reading. They were short, but fairly well written.
BUT this area of language arts education has been my nemesis. I never was “taught” to write. I just did it. I don’t know how I knew what to do. I don’t know how in the world to teach him to write the different types of papers (is that even necessary in CM???). How do I make certain that he has the writing skills that he will need through high school and into college should he choose to go?
I’m very uncertain of my own abilities to teach him in this area, so I need some real life examples and ideas to help me work through this. Honestly I’m still wondering whether I should allow him to continue on with EP online for this area, while he participates in all of our other SCM read alouds for science, history, and literature.