I can’t play barre chords at all.
When i was guitar teaching the ting that got people into barre's most effectively was
concentrate on the fingers that are not the barre first, get those to nail down
once they are doing it, with panache, add the barre
the reason this works is
starting with the barre you are pinching with thumb and one finger, one muscle does all the work.
starting with the other guys you spread the load across the hand before the barre is made.
some people do it instinctively, i didn't myself.