Controlled crying - 8 month old baby

Hello,

I am new to this site but desperately looking for some advice in regards to getting my little boy off to sleep. He has always been very aware, loves being awake but gets tired very quickly. Up until about 2.5 weeks ago he had a bottle to fall asleep, but sometimes he wouldn’t fall asleep and we would spend quite a while rocking him, he would scream and fight us not to sleep but eventually gave in. we then found the bottle had become a sleep aid and he was waking up much more in the night and getting him off to sleep was becoming more dfiicult with him screaming and arching his back for 10 minutes or more, we tried putting him in his cot and staying with him until he slept but the sight of us just upset him even more. I’ve got a routine in place now, he has milk as soon as he wakes up and isnt awake for anymore than 2-3 hours at a time. We now put him in his cot and check on him after 5 mins, then up the time by 2 minutes every time until he’s asleep. It never takes more than 10 mins for him to fall asleep, but he REALLY cries and it’s heartbreaking. Are we doing the right thing? We don’t know what else to do, he cries if we rock him and cries if we leave him, but seems to be more distressed when we do try to rock him - we really want to steer away from rocking or any other new sleep aids, he also will not accept a dummy but does have a white noise toy which seems to help. any advice welcome thanks