I'll start by saying I'm.not an expert.........
But I have done gw with ds. We Co slept from 7wks, then started putting him asleep in his cot once he was rolling and Co sleeping from when he woke up an hour later
Just before 12 months, he stopped falling asleep on the boob so I had to do something different. I started giving him cows milk in a sippy, after his bedtime routine, and cuddling to sleep. It took about 4 nights before he was more interested in the milk than bf. At this stage I gave him the milk, put in cot awake after bedtime routine (bath, pj's, sleeping bag, stories, milk, lights off, mobile on - lightshow)
The first few nights I stood over the cot patting singing etc to prevent hysterics. Then I was poorly and spent the next few nights laying on the floor patting through the bars. Then sitting, then moving away. I did it very gradually, probably took me two months to get to being outside the room. Occasionally I'd go back to sitting next to him.or cuddling on a couple of occasions if he was ill or teething.
The first night took 60 minutes. With a couple of weeks we were down to less than 30. It takes between 10-20 minutes for him to fall asleep now, but I lay him.in the cot and he rarely moves. Just lays, watches lights and drifts off.
Doing this has helped him learn to resettle himself, and night waking have petered out. He's 18 months now, and does wake up very early between 4.30-5.30, but sleeps through til then from 7ish. I bring him into bed for an hour or so after he's woken.
I've taken MUCH longer about this than most but we've had no tears which is great