Oof, that's a difficult one. Honestly my first advice really would be to just go in feet first and commit yourself to finishing that work. Not to discourage you, but it's one thing to know how to write a good start, and to find your writing style - it's a whole different task to know how and where to end things, and to be able to really grasp how to weave a storyline. The latter is a very important skill, and I think the thing artists look for as well.
It will also really boost your confidence and writing skills in general, and I think that it would help you in more ways than just collabs.
In my experience artists aren't really keen on jumping into a collab, so just try to apply to the artists that are looking instead. And be lucky 