In order to discover the style I felt represented my thoughts best I had to explore a lot of literature and music and I found Jets to Brazil and anything else Blake Schwarzenbach does basically is the kind of style I enjoy and as far as literature the Beatniks specifically Jack Kerouac are the writers that inspire me greatly. So it's definitely a matter of exploring yourself and researching others in order to create something that's your own. It takes times and I'm far from finished so just let yourself progress as naturally as possible or unnaturally if that's what works for you best. I'm sure whether you write songs or books it'll eventually begin to feel more your own as long as you keep at it. You mentioned you like to try and brainstorm topics that you feel strongly about to write about which is always a great way to begin just never restrict yourself to one specific thing unless to you it is absolutely the only thing you could ever feel yourself writing about.
Actually I take that back. I do have my own style. I like to write kinda vague with my wording so people kinda grasp the meaning of the lyrics their own way. Also I never use words like he, him, girl, she, guy, man, woman. I always say you, therefore when people read it they aren't barred from the subject that might be on their minds. Read a couple of my songs and you'll see.