Your fingers and notes when you play must have context to one another. A single note on its own merely sounds loud or soft or whatever in-between or extremity you want to imagine. How you make notes interact with one another to express a particular sound or "tone color" as one might poetically put it, requires that you understand the phrase of music you are playing and its context to the entire piece as a whole. Once you understand the duty that each part of the score must play then you can understand also the parts of your hand that must produce it. I still find it amusing when I teach students and ask then to play a third interval with one hand and make one finger louder than the other. Some find it an impossible task, and thus one needs to learn how to balance your hand to produce different volumes in the same hand simultaneously. There is no real shortcut or method I can describe in words because it all depends on how you play personally and the music that you are learning.