I have a 4 month old who I have tried a few things with, as he could only be put down fast asleep with a very awkward armed slow put down into the cot and unable to settle. He also needed to be rocked for every nap with reciting the alphabet and a word to go along with each letter or he simply wouldn't go down. He was also sleeping in the living room perched in the breastfeeding pillow next to me for 3 months.
Currently he is napping upstairs on the bed after 20 minutes of silence and sucking his fingers and drifted off by himself as he does now for every nap (past few weeks) and tonight he will probably go down to sleep without as much as 2 groans, not cries.
One day he would. Not. Sleep. And I was by myself so just couldn't do it anymore, all the rocking was doing my back in and he was screaming through bath and feed so I put the monitor on and just left him there ready for bed in cot to go take 5 mins. Within literally 1 minute he was asleep. I had not NOT rocked him to sleep once at that point and that was a month ago.
He started getting slightly fidgety in my arms aftert his when rocking to bed and I thought, maybe he wants me to piss off sometimes and give him a minute (which up until then I hadn't done at all, pure rocking, singing, stoking forehead). He took about 10 minutes of half cry half grumble then fell asleep. I tried this in cot upstairs instead of pillow next to me where he'd usually be, worked a charm and it's been cot ever since for naps.
Firstly a dummy is a necessity in our world, I'm EBF and it has helped massively at him settling by himself which was not my original plan at all but I followed his ques, although will probably be lambasted on mumsnet because they "aren't ready at this age" - he definitely was and it's good for baby to know how to fall asleep by themselves if possible, why not set them up for less stressful interupted sleep if you can?
Secondly this worked for me when I believe the past 2 weeks he had been having a sleep regression and he also has a tooth coming through, very unsettled and not a happy boy. You read everywhere Nap, feed or change and Vice versa, play, then sleep - no. For us this resulted in crying before naps when putting him in cot to settle upstairs. Infant wake, play, change, feed, (then teething gel) then straight down with dummy and comforting words. Barely a peep, no crying, happy little boy laying there for 20 minutes and then drifting off. I think the full belly for naps helps (him at least) and gives some wind down time before the sleep.
If you've tried everything and want to try something new, seeing how baby reacts to being put in cot or middle of bed if safe and left for 15 minutes after nappy, feed, wind down, at least an hour since wake up depending on your baby. I did it accidently due to unable to cope with another scream while I rocked him which now I look back and think he wanted some space maybe to absorb the world around him - within a month I put him down for all sleeps, naps and bed time, barely a fuss, upstairs in cot or on double bed in middle (pillows as buffers with monitor on) after play, clean nappy, feed, dummy in, off to sleep. Occasionally there is a one minute not really a cry but loud cat noises before he goes radio silent and I can see him playing with hands and chilling before drifting off.
Before I was wondering if I'd be rocking him to sleep every day ever until he was 2. Some people are happy doing that but I don't see the benefit to the parent or child just resigning yourself to that for years when within a couple of days or weeks depending on your child, falling asleep by yourself is a critical skill to have and yes all babies are different, but it's nonsense to say it's evil or wrong to help your baby to manage to fall asleep alone with some little cries here or there at a perfect age such as 3 to6 months before they are fairly set on their routine and preferences.
I will also add when I needed a break I let my mum and dad settle him to sleep once when I was rocking him all the time and their method was in pram, hand on chest whilst he cried, and dummy back on every time he popped it out. I was struggling and happy for someone else to do the sleep routine without me and was shocked he fell asleep without a rock. That may have helped him get to the program slightly and I didn't need to be involved and listen to him cry but trusted my mum and dad with that task and to be honest I'm millions better off for it.
I had a terrible back in pregnancy signed off work for 2 months and bed bound for the 4 whole months so couldn't deal with rocking forever like some people are happy to do.
Hopefully anything I have mentioned works somewhat for you, if you have any questions feel free to ask me and I'll give more details. Signed mum of boy who is now snoozing upstairs after falling asleep without any tears or rocking and who seems much more happy for it!
Oh and CBA to scroll up but feed directly before put down for nap took naps from 30 mins to one hour/2/3 hours in the past couple of weeks. Before his regression, in the pillow after a rock he would do anywhere from 30 minutes bang on to 5 hours napping on the pillow.