You may not be using the "special words".
All of the sailors I have seen use this system have a few "special words" that they say softly at this part of the process. The longer the process takes, the louder and more forceful the "special words" get.
The "special words" appear to soak into the sail and after a while less of them are required. Obviously, when you get a new main a lot more "special words" are required especially for the first few attempts.