It depends what you understand by the term dystonic finger, as you can get a whole range of unwanted flexions and extensions in different fingers (and it sounds like this is true in your case).This 'chain reaction' of unwanted movements becomes habitual, so really you are retraining your whole hand to work again properly. I have included the little finger C, for example.
I found that fingers that were overcompensating settled down fairly quickly when I exercised them in different combos (without the finger I had lost control of). Fixing the M dystonic finger (M) has taken a lot longer and has involved all the combos you mention and a lot more too. Some movements have always been harder than others, and I have found when hittinga rtick wall its best to go round a problem than attempt to battekl through it. Its also better to break down complex tasks/movements into their simpler components and work on them.
