I'm still a relatively new player myself (haven't hit level 4 in anything yet, but close in all roles).
That said, my usual routine is to ask in the lobby if any of my crew have mics, and to only use voice when someone I'm with is also doing the same. Also, at the beginning of a match, I tend to start with just a quick weapon overview and "any questions, feel free to ask. I don't know what I'm doing."