In school for fun when it was boring I many times would do writing exercises with the right hand (like write a line of A's, a line of B's, etc) and after a coup

In school for fun when it was boring I many times would do writing exercises with the right hand (like write a line of A's, a line of B's, etc) and after a couple of weeks I got the right hand up to maybe 80% speed and accuracy of the left, but I realized I needed to do constant training to keep it as good as the left (admittedly the left had daily training of many hours due to having to take notes, etc). But it does sound plausible!