The herbs that will enhance breast size are Saw Palmetto, Wild Yam and Fenugreek. There are breast enlargement pills that contain all three, that seem to have good reviews. However you can buy all three herbs individually for a lot less.
Massaging your breasts, I'm assuming, is a form of jelqing, which is done in many cultures by men, since the beginning of time, to increase the size of their member. I have a friend who was rebounding (using a mini trampoline) as exercise and claimed that her bust was increasing in size. This is the first thing I thought of.