Self settling's definately not a myth but I firmly believe some kids are naturally better at it than others. Question is, can you turn a non-settler into a settler? Good sleep is 90% habit, I feel, so perhaps he's got himself into a "bad" habit? I'd suggest that the most important time of day for him to settle himself is at bedtime, then hopefully after a few days in a row of doing it then, he would more naturally be able to follow suit overnight. Can you get any help from sleep counselling-trained nursery nurses through your local health visitors?
My DD is now 4 and I've an almost 9 week old DS. Couldn't be more different in lots of ways especially sleep. But I am different too and this makes lots of difference - I had the view with my first that she must never, ever utter a cry otherwise I was being a bad parent. So every time she did cry I stuffed a boob in her mouth, mistaking every cry for hunger. I rocked, held, swung, fed or walked her to sleep and spent, literally, hours moving her slowly from breast to bed, starting the whole feed to sleep process off again if she woke "on transfer". My husband didn't see me for months during the evening, which may account for some of our problems now! By the time she was 3 we had such a huge sleep problem with her that we called in a night nanny.
With my second child, I'm totally different and much calmer. I accept he may cry and sometimes I will not understand why and won't be able to do anything about it, but that's OK. Babies cry. I think he's picked up on me being calm, so he is too. He settles himself without me trying, really - I just popped him in his cot just now whilst gathering nappy changing things, turned around and he'd gone to sleep.
Inevitably while I've been cooking tea / peeling DD off the floor after a fall / doing ten million things at once, there have beenlots of times when a tired DS has been left sittingin his bouncy chair shouting the odds and eventually has given up and gone to sleep. I'm sure this has helped him do it at night too.
I hope some of that helps!