I'm a big believer in trying to break difficult techniques down to simpler parts, and trying to practice those separately, then putting things back together slowly. I found the first exercise on this page
http://www.guitarhabits.com/effectiv...s-sound-clean/
to be helpful in isolating just the index finger - letting you experiment with where it needs to be placed, what angle, what overlap. etc.
And it's a strength-training exercise too, building up the index finger by practicing with it in increasing difficulty, then decreasing. It's always good, when learning something, to have something you can succeed at, rather than fail, so you get a sense of progress and achievement. Barre chord practice can take that away, if you're not careful! -)
Good luck/hang in there/when you're ready, find a tune with just one bar chord in it and work on that. -)