In my experience, partial harvests never work.
Just harvest all at once and accept it as it is.
Smaller immuture buds are great to give away or use at parties where no one really cares because they are drunk anyhow.
Removing large parts of a plant (partial harvesting) causes a huge metabolic shock to the plant, meaning it never fully recovers and/or has enough health/vigor/energy left to continue ripening anything left over, properly.
Second pick buds never have the same quality as buds harvested all at once, even though they may seem a bit immature, in my experience.