I have had some trouble with bar chords as well, but a song that really helped me out was sublimes song Boss DJ, it is mostly just G and C but then near the end it switches to a bar G (third fret) sliding to a barred A# (sixth fret) and then proceeds farther up the neck to a barred C (eighth fret) and a barred D (tenth fret), this gave me alot of trouble at first, especially the root C to the barred G, but after I got that down it seemed so much easier to do bar chords on just about every song, and its a very fun song to play. To this day I find myself playing it all the time around camp fires and such, even though hardly anyone who isnt a sublime fan knows it, its still a crowd fav 
anyway, just thought I would throw this out there for you, maybe it could help.
-BC