Seconding tape! I have what’s considered to be a larger chest but mine are not very dense. I’ve noticed that helps me a lot with getting my chest to look right with trans tape. From what I’ve heard/seen online, tape is harder to use if you have denser chest tissue.
The other thing I do in hot weather is wear a moisture wicking under shirt under my binder. It helps a lot with general sweat and making sure things aren’t too swampy under there. I like the Uniqlo Airism shirts, but anything moisture wicking and thin will work great.