i honestly think it's not possible to shut it up, nor is that the goal. For me the goal is to accept that it's there; as i think it's always there in all human beings...
i call it Radio Station WIIS (what is it saying?) and the only thing to do is notice that it's there, is always operational, and let it be.
i also notice that at times, a state of quiet mind can be present. when it is.
but i don't make WIIS wrong, nor attempt to impose force on it, or try to make it stop. that never works... (remember the one about the mom who told her kid "Now whatever you do, don't
think of a monkey!!!")
i just notice when it's there, thank it for sharing, and go about my business. resisting it only makes it persist, and louder. so at this point i've come to accept that there's a radio station in my head, and that it's part of the human condition.
and while i do realize that could come across as flippant and jokey, really i'm absolutely serious.