I have, using Handwriting Repair by Briem. It was less work than I expected, and my handwriting looks pretty cool now. Even if you don't adopt the italic style advocated by the book, the other advice is still generally useful. I printed out the tracing page and did that a few times a day for a few days to get familiar with it. After that, it took a while, but it eventually became natural to write that way. The italic style helps with writing fast.
I used the book "The Italic Way to Beautiful Handwriting" by Fred Eager. The italic method, in contrast to printing or cursive, seemed to have enough connected letters to write quickly, but without insisting on connecting everything like cursive, even when it made writing awkward. I also followed some of the movement drills from a manual for the Palmer method, a cursive pre-typewriter "business" handwriting style from the early 1900s that was meant to be written quickly and legibly all day, but which some folks think looks too old-fashioned today.
One tip is that you need to train your eye as much as you train your hand.
First redo your grip, it probably sucks.
Then relearn the alphabet using that grip to the standard of your eye.
Then relearn to see the flaws in your handwriting in increasingly subtle ways and keep training to eliminate those flaws up to the standard of your eye.
I took a calligraphy course when I was in uni. Interestingly enough by a Japanese woman. City I went to school in also has one of the largest Japanese communities in Europe and a even a few Japanese crafts/pens/office shops. Article definitely rings true.
If you have a university close by that's I think a decent place to start.
I massively improved my handwriting with near daily practice for a few months. Just the alphabet and various words (stuck with print, not script, so limited need to practice hard letter sequences). Pretty much just filled legal pads with letters and some words until my handwriting was to a level I was happy with.
It’s like playing a piano. Start with slow tempo and get everything right. Then gradually speed up while maintaining the quality. And at a certain point it is not possible to write faster without changing the shapes of letters to be more cursive like, and that is ok.
https://sites.google.com/view/briem/free-books/handwriting-r...