For me, i couldn't bear to hear my child cry. It was like a primal thing, i just could not cope with it
He was a super high needs baby (reflux, allergies, eczema) who woke every hour until 18 months
He needed to nurse to settle, otherwise he'd cry until he vomited
I co slept and fed to sleep until 2.5, and fed when he woke up (very short feeds every few hour)
At 2.5 he was old enough to understand " No milk until morning" and he'd accept a cuddle at night time wake ups
Shortly after, he started to sleep through
Once i stopped nursing, at night, getting him to sleep initially, I'd lie there for a little bit and then say I needed a cuppa or quick wee and leave for a bit. He'd often just fall asleep then.
This naturally evolved to him falling asleep listening to a read-aloud story
So, no CIO, no specific plan, it just happened
Maybe not the best method, but what worked for us and what I felt he needed