It takes time and its a really, really brain dead stupid idea to overdose on estrogen to try and expedite the process.
First, an overdose of estrogen will in most people result in conversion to testosterone.
Second your breast grow they "fuse" after a period, You want the growth phase to be long enough to get as much growth as possible.
A good few folk I have met overdosed and ended up will small, undeveloped cone shaped breasts - they all really regret it!
Another thing is that the "fusing" bit is not hard wired for everyone. In the maternal line of my family, we develop then have a second growth spurt in our forties. I am lucky enough to have gone from a C cup in my twenties to an 36E in my fifties with the spurt not that long ago.
Shape and size are inherited, as are size and sensitivity of nipples and aureola.
My partner has been on hormones for almost two years, is between a B and C cup and still seeing growth. She is currently recovering from SRS and the stress and recovery has an impact but I can see changes almost weekly.
I have no evidence but I believe that stress impacts the process, so while I know its nigh on impossible to avoid stress, its a very worthwhile objective and it may reap more rewards than you expect.
The other bit of advice would be to avoid breats augmentation until you have had at least three years growth otherwise the bodily insult may delay natural growth. There are a good few TS who get a BA then a few years later have yo have a breast reduction - resulting in TWO sets of scars. Stupid...