Speaking only for myself, it took a few months of regular writing.
Like (perhaps) others, I had been forced to use them in grade school -- we were told that "it would improve our handwriting". It laid a foundation for fluency in cursive, but my actual handwriting was terrible.
However, when I came back to fountain pens (after a couple of decades), it was relatively easy to improve my script to where I'm happy with it. Having the "cursive" foundation probably helped a ton.
Like (perhaps) others, I had been forced to use them in grade school -- we were told that "it would improve our handwriting". It laid a foundation for fluency in cursive, but my actual handwriting was terrible.
However, when I came back to fountain pens (after a couple of decades), it was relatively easy to improve my script to where I'm happy with it. Having the "cursive" foundation probably helped a ton.