I second the things mentioned here :3.
I would recommend going for a compression shirt. I'm also a large chested girl, and have used ace bandages and I always run into issues. I have trouble breathing, and ace bandages will tighten over time so it can become dangerous (I've actually heard of people accidentally breaking ribs this way x.x...). So compression shirts are worth the money and much more effective :3.
Cosplays I've done:
Casino Rosette- Chrno Crusade
Train Heartnet- Black Cat
Amu Hinamori- Shugo Chara
Shuichi- Gravitation EX
Maka Albarn- Soul Eater
Olivier Armstrong- FMA Brotherhood
Fem Dante- (DMC1-closet cosplay, plan on making original designed costume)
Rin Okumura - Ao no Exorcist
Cosplays I'm working on:
Demon form Rin
Levi -Shingeki no Kyojin (Three different versions; 'mr clean' Levi, regular, and formal for Katsucon ball)