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I did very similar to lenibose. Gradual Withdrawal as an over-riding parenting ethos from birth. As in I planned to always give my baby enough reassurance and comfort to not need to cry at bedtime at all, but always with a view to eventual independent sleeping.
She was about 12/13 months when she got to the point where I could put in cot (with dummy and blankie) and she would go from fully awake to asleep alone without making a sound.
She has never, ever cried at bedtime - so this was teaching a baby to go to sleep without me leaving her to cry. It took about a year to achieve, and that is from birth so without any pesky 'bad habits' (BF to sleep is not necessarily a bad habit, it depends on your view and if this is a problem to you, or not)
Oh- and have tried switching boob for dummy and no deal. She spits it out in disgust and roots for the boob.
Yeah, they do that. Definitely worth the perseverance though.
However 8 months old may be too late to introduce a dummy so you may have missed the boat there.
If baby likes to suck to go to sleep you could try encouraging her to suck on a blanket or toy comforter? Otherwise, unless you go the very, very, very slow route, you are likely to encounter some crying as she falls asleep without a nipple plugging her mouth.