@LittleMG
If it helps, this is what we did.
I cut breastfeeding at night cold turkey. He was waking constantly and couldn't get back to sleep without it. He did not need it for nourishment, it was purely comfort. He has always taken a dummy for sleep so I knew I had to focus on that being his comfort.
I left a sippy cup of water in his room and every time he woke I went through and offered it to him. He'd shove it away in frustration and cry for breastmilk. I comforted him and continued to offer the water or his dummy. After a lot of fighting and crying with me he'd take a big drink of water, accept the dummy and go back to sleep.
It took about 4 days of doing this every time in combination with pick up put down method.
So it looked like this:
When he woke up I'd go through to his room, put on a soft night light and offer water. If he didn't take it I'd say "ok I'm going to put your cup here next to teddy" (he sleeps with a favourite teddy) Then I'd pick him up, give him his dummy, and cuddle him until he was calm. Then put him down. He literally spring back up again and stand at the bars of his cot crying. So I'd do the same again. I'd give him 3 times getting picked up and cuddled and put back down.
If he stood up after the 3rd time I wouldn't pick him up. I'd just lie him back down. He'd get up. I'd lie him back down. Repeat repeat repeat. I'd say "shh it's time to sleep. Mummy and daddy are going to sleep. It's time for you to sleep." After 3 times of this I'd just lie him back down each time he stood up, now not saying anything. Just shhhing and stroking his head or back.
It could take 50 times of doing that over their cot bars. Back breaking. But if you keep your resolve they will realise that this is how it's going to be from now on.
Now, if my son wakes in the night he finds a dummy by himself. If he can't find one in the dark or if he wakes for some other reason, one of us goes through and turns on a soft night light and hands him his cup. He takes a big drink, rolls over and gets a dummy and goes straight back to sleep. He usually sleeps 11-12 hours straight now.
Top tips:
Give him a supper before bed. Porridge with banana mashed through is a good one. Or a bowl of warm weetabix. That way you know they're going to bed with a nice full tummy.
Don't try to do any of this in the dark. Have a soft lamp or nightlight on so they can see you.
If he has a favourite teddy I found it helped to go through when he woke and cried and cuddle teddy first. I'd say "aw poor teddy is sad. He's crying. Shhh shhh it's ok teddy". Then I'd pretend to give teddy water and a dummy. My son would watch all this, through tears, and then want to take the cup and dummy for himself. Then I'd do the same for him a cuddle and "aw you're feeling sad, it's ok. Shhh shhh time to go back to sleep now with teddy".
If you're breastfeeding do it yourself. We had short term success with his dad going in instead of me. But then it fell away and I started breastfeeding again after he got a sickness bug. I realised second time round I had to do it myself because I wanted him to realised mummy was also saying no more breast milk.
He is breastfed now only before his nap and before bed so he still gets that comfort and it's linked firmly to going to sleep. But he goes to bed awake and chats away to his teddy and settles himself.
Good luck to you and to OP. You can do this. You are not neglecting your child. You're there with them the whole way.