Well foremost, my arms get big quick. Always been that way. In fact, I don't even have bicep days bc whatever upper body exercise I do period, my biceps grow. But obviously the rest has to match proportionally.
So it's really everything else regarding the upper body, like I said, I went hard at the gym on my days off, then at night on the floor in my house doing kettle bell workouts and pushups til fail. Fix my protein drink mixed with some frozen fruit, peanut butter and honey (sometime chia seeds for extra protein) and creatine mixed in.