According to "urban dictionary" - "been there done that"
Joan, I can't tell you what your way of integrating will be, but I can share mine. When one of my others is ready, I picture her (or one day it could be a him) as clearly as I can - and sometimes by then we're already starting to blend, so I can imagine her and feel her at the same time - it does feel like a joining together of essences. My T always asks me to imagine holding her. Then I usually do something that came to mind the first time I did an integration - I imagine taking her into my heart - the heart centre or chakra, not the physical heart, level with the physical heart, in the centre of the body - and from there, feeling her separate self dissolving like light into my heart and body, then I can feel her in all of me, but she feels like "me" now.
Sometimes just before integrating, either the other one or I will have a moment of fear and have to ask my T whether it means that the other one will die - and she reminds us that it doesn't mean that, it means that we will be part of each other and will always be together.
After integrating, I don't feel the other one like a separate part. It's more like I feel within myself the qualities that that alter had - eg I've been able to stand up for myself, to express more, different kinds of feelings - that could be what happens for you when Mouth becomes part of you. I've felt stronger, more solid, more whole - if my head's been fuzzy, or I haven't quite been "in myself", I feel very different after an integration - clear-headed and very much present.
I know there are "natural multiples" who say they don't want to integrate because they aren't spilt-off parts, but I'm one of the ones who started out as one whole (as far as I know), and split because of trauma, so for me it's natural to integrate, and it feels right. I've posted elsewhere about feeling a real strong feeling of hopelessness and despair, and realising it came from an alter, and after finding out which one that was, and integrating with her, I just didn't feel that any more. My T explains that when you and another part become one, you share the feelings and memories, so you can think about them and work through them. Emdr also seems to jump over the dissociative barriers and help the split-off feelings to move from the amygdala (part of the brain) into the neo-cortex - front brain - where they can be thought about, felt and processed. She does integrations with me while I'm holding the alternating buzzers, which seems to help it all along, but as Una wrote elsewhere, it isn't always right to use emdr with DID or DDNOS. The integrations I've described are pure ego state therapy, and can be done without bilateral stimulation - I've done them with therapy clients, and they seem to work just as well, and to hold, when the host and the alter are both ready. Joan, you don't say whether you're in therapy - I don't see why you can't integrate on your own, since Mouth seems so ready and is asking to integrate, but please don't do anything that I've written about unless it feels right to you and to your whole system. It's my personal experience; only you can know what's right for you. So please listen to yourself - and let us know how you are!