Lots of folks here have already mentioned about practicing! And, I too, have to agree! There is no short cut to barring chords, but there are exercises that will help expedite learning! As well as reducing cramps in your hand.
Start with either squeezing a tennis ball (left hand) or use a spring-loaded hand grip for guitarist. This grip exercises each finger independently. So, focus more on your index finger and thumb!
When practicing, I would suggest you not use your thumb, except for placing it behind the neck. I know a lot of musicians use theirs, but if you are to learn correctly, this would be the best way.
Keep at it, and you'll see improvements in no time.
i can't seem to get both the b and the e when i do the thumb over barre chords. so i fix this by either choosing to press one and mute the other. my question is, which is better to play? on the G bar chord, i've noticed it doesn't sound like an open E chord without the e but i noticed the A doesn't sound close to the open A while pressing the e.
i know that an alternate fingering to the F is to do it without the high e, does this apply to every bar chord? should i just play the e on certain chords and play the b on others?