I found bar chords completely impossible at first, it was completely bizzare how people could do it so easily. But over a few days something clicked, and suddenly I can do them without too many issues. They still take some time to apply, but I know that can be fixed with practice... I thought I might share my recent enlightenment so perhaps one newbie can help another
. Of course, please do not put too much faith in my suggestions.
I think the key realization for me was that there is no magic bar that will make all the notes sound out that you can use all the time. Its better to just pressure the notes you need to use, only for the length of time you need them. Often you will only need 2 notes. So for example in the first two bars of Sor Op 35 22 you actually only need the bar on one string once in each bar for a short period of time. So you need to figure out each bar on a case by case basis. If you are lucky a well-placed knuckle or two will get you there with absolutely no effort. Sometimes you will need to use the soft bit of the finger (the strings dont work out) , then you will have to use more force, but only for that short length of time.
Everyone's finger is different, so its probably a matter of trying to find it out for yourself once you know the basic ideas. I kept trying for a couple of minutes a few times each day, each time I will naturally do something slightly different, and some of them work. Over time the hit rate goes up, and then suddenly you will realize the trick and then its all good. If it doesnt work within a couple of goes quickly give up and come back again later. No sense in squeezing harder and harder practicing the wrong thing; if the fingers are tired and cramping after two minutes then you are definitely doing it wrong, and even if you were to get it right it might not work if you fingers are cramping (or worse, it works only if your fingers are cramping
1) I think the rolling the finger trick is good. Sometimes bending the rolled finger seems to help too, maybe the extra torque from the bend, and also sometimes closer to the fret.
2) The "depth" of the finger (knuckle position) is crucial, so try many positions. Also, theres two knuckles, sometimes running the finger at a slight angle (i.e. not parallel to the fret) can help place the two knuckles in the good spots.
3) Putting the knuckle (base of the finger) higher and having a straighter finger helps if you need middle strings. If you want the end ones then a lower knuckle and a more bent finger can be better.
4) The finger position is obviously easier when near the fret, but it doesnt actually matter all that much once you figure it out.
Finally, you must absolutely believe that a solution exists, the only (easy) problem is to find it. Maybe it is harder if you do not have a RulerFinger, but is is possible. I think I only made real progress after I stopped bemoaning my finger shape. Now I think my finger is actually quite ideal for this!