Honestly, I don't even think about it anymore. It's not so much how you breathe in, but it's about starting your breath before you start speaking. You have to be exhaling for your vocal cords to work. While I was learning to speak fluently, one of the key aspects was not closing my lips together for any sounds or any reason. That while I was speaking that air had to continue to flow out my mouth. Early stages of fluency development was a lot of mush mouth. Continuous sound. It sounded weird as hell but at that early stage it was just me and the therapist. But it was practicing fluency and learning to speak without any disfluencies. Later in the development was when we transitioned me from very abnormal fluent speech to more normalized flufluent speech.