How do you write Dramione fanfiction when you haven't read Harry Potter in ten years?

Hi, I haven't read a harry potter book since I was a young but I want to start writing Dramione fanfiction. I've rewatched the movies recently, and have ideas for fics, but I can't remembering the books as clearly as I did back then. If I were to re-read all the books it would take me months and I really want to start writing Dramione right away. Any tips on what I could do, or you go about writing when you can't remember the books very well?