Disclaimer: First time poster, long time lurker.
I've only been dealing with this for about 6-8 months now, and I'm small (38B/40A) but while struggling to find my interim solution (I will inevitably opt into surgery if the Endocrinologist can't help me) I have tried a
lot of things. So far I've found that simple compression bras, like Fruit of the Loom sports bras, make me the happiest overall.
I have a couple compression shirts, one from Underworks and one from Spanx, but I generally dislike wearing them. The Underworks shirt is more effective, but it's way too long for me, it covers me down to almost the bottom of my briefs, which makes commonplace tasks a bit unbearable. The Spanx shirt is less effective for the chest, it seems to be more geared to belly flattening, but it's more comfortable overall and I can tolerate it for much longer. I've given up on the Underworks shirt altogether and only wear the Spanx shirt when I need something that looks "proper" with dress clothes, like a white shirt and tie scenario. By the end of the day, though, it has to come off.
On the bra side of things, for me it depends on what I think I need for the situation. I have a couple Underworks "Extreme MagiCotton Sports and Binding Bra"s that are extremely effective, and I'm talking about a completely flat chest here, but they are so tight they hurt my back and after a couple days of use cause chest pains as well. The neckline on these garments is high, you will see it under a normal button-down shirt, but it's very t-shirt like in appearance in my opinion. I also have a few Coobie and Bali seamless bras that feel great and are pretty comfortable to wear, but they are encapsulation bras and make me look/feel too feminine -- I want to hide the "girls", not showcase them. I've never worn these outside of the house.
My comfort zone right now is with Fruit of the Loom sports bras (sized models, not the S/M/L/XL ones) and the Champion C9 sports bras available at Target. The Fruit of the Loom model 9012 - "Women's Tank Style Sports Bra" is pretty tight under the arms and can't be worn all day, but if you can tolerate that it's pretty effective. The Fruit of the Loom model 9036 - "Women's Strappy Sports Bra" looks more feminine in the mirror but provides a less uncomfortable experience for me and equals the effectiveness of the model 9012. I have also found that the Champion C9 sports bra available at Target, perhaps exclusively, is an equally effective and slightly more comfortable version of the Champion "Infinity" sports bra. I have three of these - one Grey, one Nude, and one White. I won't wear the White one as it's too tight, but the Nude and Grey fit very well.
In summary, I like bras much more than I do compression shirts, but having a compression shirt or two is a must for certain situations.
I sincerely hope you find a solution that works for you, and I hope that you post it for us to see, it may just end up being the silver bullet some of us have been looking for