You haven't mentioned it yet so maybe you are already are doing "dynamic" balancing.Yes this whole thing is tricky . A ton of trial and error going on . I try extra loud and extra quiet to identify anything poking out in the mix . In effect I've established in my mind that reducing one component then alters (increase) what else in the mix is coming through . Ultimately it's a compromise. Arguably if one component is very slightly proud in the mix it might be best to leave it rather than throw out the whole balance . This I think is partly where the whole repeat climb down in levels comes from in my case . Unless further eq might solve that it I guess . Have made fair improvements in any event .
If you don't already know, dynamic balancing is using automation to feature different parts at different parts of a song. Volume, pan, eq, and compression changes to highlight different things using automation