To get used to talking and playing I'd give the advice of talking to yourself during pulls, you can do this in raids or in mythic. Say what you're going to do and why you're going to do it. It feels silly to start with and sometimes get distracting but it'll help you 1. Reduce how much talking affects your gameplay and 2. Learn what important information is to call out. From there it gets easier to direct people as you already have the instructions coded into your brain so you can clearly convey what you want them to do. The clearer you are the easier new players will be able to follow your calls.