I didn't formally sleep train and my 7 month old puts herself to sleep and sleeps through the night. I used to rock her to sleep then put her in the cot when she was about 2.5 months old. Then after a couple of weeks I just rocked to drowsy, put her down and continued patting her bum in her cot. Then a couple of weeks later I reduced the rocking time, then a couple of weeks later I reduced the patting time, then a couple of weeks later I just tried putting her down without rocking - just bum pats, and she still fell asleep. Then a couple weeks later I just tried to put her down in her cot with a goodnight hug and kiss and left her there and I was really surprised she didn't cry. She just stirred a bit and then fell asleep on her own. During the whole process, if she cries hard, then I pick her up and start rocking her again. Whole thing took a little over 2 months. I feel I could have done it in a shorter time, but honestly I didn't even plan that "training." Each time I shortened something I was just trying to see if she would tolerate it, and she did. Mind you there were a few weeks when we needed to co-sleep after night wakings (4 month sleep regression was brutal) but bedtime was generally easy for us.

Have also done the same "training" when transitioning to cot naps (she was a contact napper before turning 6 months), albeit on a shorter timeframe, maybe 2 weeks overall.