This may be too obvious, so forgive me if it is.
My biggest problem with flex nibs is retraining myself to use a lighter touch. We read here on FPN all the time about how nowadays everyone is used to bearing down on their pens (hence the pen manufacturers' reluctance to make flexy ie fragile nibs).
I have some experience with dip pens which put the flexiest fountain pens to shame, and even so when I first started to use my Emotica I had a lot of trouble getting it under control. I don't know whether my brain shifts modes when I pick up a fountain pen, or maybe I expect to have to pay attention when I'm using a dip pen. Whatever it is, even with my experience with much flexier pens, it is difficult for me to modulate my pressure adequately.
I have a few suggestions. First, get a Kuretake or Kamei... heck, even a Pentel brush pen (not one of the flexible markers, I mean a bristle brush for a nib) and practice with it. You may never get to where you can write in a notebook with it, but when you come back to your flex metal pen it will seem much more manageable.
Second, practice on a table, not in a notebook in your lap. Get a table that is stable and put down some paper flat on it. It could be a pad of paper or whatever, just so it lays flat. Practice putting down lines with
less pressure than letting the full weight of the pen rest on the paper. See how lightly you can draw the nib across the paper and still get a line out of it. I say make sure that the paper is laying flat because the slightest bowing or bulging will completely change the line you get or if you get one at all.
Check these out for practice guides, and have fun!
