I was a switcher as a kid, when I chose I chose left but it irritated me (getting ink on my hand all the time, having pens clog etc). Now I write with both hands. It probably took about 2 years to become fluent but only about a year to become decently legible. Signatures are funny because I’ve had 2 variations and they are the only thing I can’t vary properly. LOL. Weird.
Not sure how I could help. This is one thing only practice will help in. Good luck.