Modifying your current penmanship
Learning a new style of penmanship
and
Learning how to use new writing tools
are 3 entirely different things.
Putting your nibs and ink away while you focus on penmanship will not give you any advantages when you go back to the nibs and ink.
There is no shortcut for learning how nibs and ink work.
My experience has been that people need to experiment and try a variety of things - and not be so focused on a specific result.
Enjoy taking some new paths - other people (including me) can tell you what worked for them -- but none of us can predict what will work for you.
If you posted some samples of your penmanship - those of us who have taught can offer suggestions.
@Zivio is soooo right -- you have to find a nib-ink-paper combination - and that will be a very personal choice.
While some people enjoy printer paper -- some of us prefer Rhodia and Clairfontaine.
While some people like Higgins Infernal - some of us prefer walnut ink and McCaffrey's
Nibs -- Nikko G's are not popular with the experienced scribes - but, they work well for beginners.
I'd encourage you to spend 20 minutes a day on improving your current penmanship with your fountain pen
and another 20 minutes with nibs and ink - just getting the feel for the basic shapes. Stems, bowls, curves, compound curves, etc
and - if you have time - choose a brand new style - and start practicing that one with a pencil.
My 2-cents.
If I find time - I will go back and search for some of the before and after penmanship of people who took time to post images to the forum.
There are at least 4 that I can think of who made remarkable progress -- by posting their work.