The way I play the B-Major (and B-Minor, for that matter) is I fret the A String on the 2nd fret with my index finger (not using it to barre across the other strings), then fret the other three strings like I would normally fret a Power Chord or A Major/Minor and only play the 4 middle strings (I use the finger on the B-string to also mute the e-String so it doesn't ring). Works pretty well for me so far.