Just an update - DS2 turned 5 weeks today and I started yesterday with patting in the crib, no shushing was needed with dummy in his month. I stuck through the full 10-15 mins for the first sessions.
Today for all his naps, he went down independently after the 4s. I personally feel that sleep training after a month really works as DS2 seems to have progressed in maturity and seems to understand what we are saying. The wind down was important and reading the cue when your Lo is tired, ie the sleep window.
It is early days but having adopted BW techiques with my 2 much older kids, I am a believer that it works. Keep the faith!