Sometimes scribing for a bit can help to tease out the nature of the errors. When I scribed math for my dysgraphic-esque #2, I specified that every step would need to be verbalized, including regrouping (which digit to "carry"), parentheses, etc. For self-monitoring, we emphasized the meaning over the procedures. E.g., our key work-checking points were 1) did I answer the question, 2) does my answer make sense, and, 3) does my answer have the correct units/significant figures, etc.?
In our case, removing the handwritten aspect improved overall performance considerably, both on the initial work and on error-correction. So much cognition was going into managing handwriting, numeral formation and placement on the page that there just wasn't enough executive function left to self-monitor, and certainly little motivation to do more than a cursory review of work afterward.
It helped to reduce the number of items required (what I would call "items sufficient to demonstrate mastery" when writing formal accommodations) per day/assignment, in addition to oral elaboration and scribing. I think it was also incrementally helpful to remove handwriting demands from all other subjects for which it was not the principal goal of instruction. We switched to speech-to-text (and later wordprocessing) for everything but actual handwriting exercises in second or third grade.
