You should learn to voice a chord with any finger. Here is an exercise: play 5 notes in the RH - C,D,E,F,G. Make them all sound equal. Then bring out one note a time. (While still playing all the notes).
In reality, the note you want to bring out (voice) is played at a faster velocity, but at the same time, as the other notes, but that is hard to visualize. I think of added pressure or weight on the note I want to voice. You have to find the visualization that works for you.
Do that 5 finger exercise until you can voice any of the notes. It takes time and practice.
Sam