The shoulder heated up a bit for the bench press, but was otherwise ok. Well, not ok, I can still feel some "dont go there" spots in it under load, but I've gotten good at avoiding them, and they're getting smaller.
Doing the flys was interesting. I'm supposed to "squeeze with my chest" to pull my arms up and together, which is hard, the "default" set of muscles to do that motion are the shoulders. A couple of times, I could feel the right muscles do the work, but it was erratic and unrepeatable. It felt a lot like learning to wiggle ears or raise an eyebrow, to use the chest. Hopefully eventually I'll get it. My trainer said he can isometrically contract and hold his chest muscles until they cramp.