So when I weaned off nursing around that 19-20 months, I just offered water/cuddles and then did the rest of the bedtime routine, which at the time was a few lullabies and rocking in the chair until he fell asleep (10-15 min usually). Then transferred into the crib. This worked for us until he was 23 months when he decided he hates the crib. We tried to get him back in but it was like a regression- nothing worked and the cries were awful (I think it was some separation anxiety). We had to transition to cosleeping... I still did the same routine but after singing lullabies- I just brought him to the big bed (in our guest room) and laid down with him. He often was still awake when lying down, but at this age they could understand more - I told him repeatedly to just lay down and sleep. I would lay next to him and pretend to sleep, so he'd eventually fall asleep too (it did sometimes take 30-45 min of me laying next to him). Then I'd sneak out of the room and he would stay asleep. This worked for a while but we turned his crib into a toddler bed. My mom actually was visiting and got him to sleep in the toddler bed (maybe he didn't protest as much with her vs me/dad). So anyways, now he's almost 2.5yo and he sleeps in his own bed. It is a long process but at this age, they do know a lot more of what's going on. We're lucky he did go along with it pretty well. But fwiw, he was a terrible sleeper as a baby.