I took a tantra seminar and was taught this exercise which included the breast massage. I do not always do the other breathing exercise since I injured my knee and it made it difficult to sit in a lotus position BUT, I do the breast massage very frequently and it has made a significant change in the way my breasts look.
It must be positive since I have been doing it for just over 4 years now and have taught my girl friends and my daughter how to do it. I just wish I had learned it YEARS ago! I also feel it benefits me hormonally and keeps everything flowing so-to-speak.
I hope you have as much success as I did/do with it.