The barre chords are mostly technique with just enough strength to place them. Come off the power and study the strings your index finger needs to fret. Focus on only those. Then, the idea is to keep just those strings ringing when the other fingers are fretting their respective strings. It's a dance of technique. Once you get the index finger to properly fret the required strings you need to hold that finger's shape as you engage the other fingers.
Initially, you tend to throw the entire chord shape simultaneously. Strumming requires that. If picking, however, you might break that down to placing the fingers on the notes of the chord that must sound first, following them with the balance of the fingering to complete the chord. This is encountered a lot in finger picking and it offers lot's of opportunities to cheat the chords - playing partials, dyads (double-stops), arpeggios, etc., that strumming disallows (unless similarly effected with deft use of the flat pick).
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