HELPING:

Illegible handwriting can be due to a wide range of things including hiding poor spelling or not being able to form certain shapes uniformly.
 
Adults who rely on their handwriting for their work can be helped by the Davis methods, as well as children whose writing is not progressing at school. Often the incorrect formation of letters fuels the dyslexia.
 
The speed of the ‘dyslexic’ mind plays its part here too, as writing requires precision which greatly improves when speed is reduced.

Problems could be simple to rectify like poor pen grip or lack of proper tuition at school; or there could be more deep-rooted issues. There may be a combination of many factors which need to be unravelled one by one.

Correcting handwriting is generally covered by the Dyslexia Correction Programme as it is usually accompanied by dyslexic issues.