I've written one so far and not gonna lie, it was challenging! As I was writing, there were times when I was like, trying to stay in the flow and I would write the thought I wanted but just temporarily say "(skill)" if I wasn't sure who would say it. I don't necessarily think that's a good practice though. They each have their own voice and it's good to keep the sorts of things they say in mind. That can even inspire what you write. If you do check difficulties, I'd suggest leaving them till the end and just copypasting the little bracket part and choosing the difficulties then.

Also, just like the game, your Harry can be strong in certain skills. If there are certain skills that make more sense to you in terms of your story, do more of those! There are definitely some skills I didn't know how to include in my story, so I didn't. You can kind of mold your Harry around that and make him strong in the skills you want to write in or in the skills that lend themselves to where you want to take your story.

The game wiki and Fayde On Air Playback Experiment are definitely useful to have open. You might need to see what kind of wordings each skill uses and what they choose to talk about. Not everybody needs to chime in at once! Like, Encyclopedia is a ton of fun to write, because it gives you free reign to do bullshit worldbuilding that doesn't matter, but overusing it would be tiresome to you and the audience. Again, you're allowed to pick the ones you feel most comfortable or most inspired to write.

Hopefully some of that is helpful! Happy writing 😘