Good advice there, to try using different fingers.

Also, you are doing exaclty the right thing with the slow repetition! Keep it slow. The part of your brain that is being 'trained' by these repetitive movements learns differently than your conscious mind - so it may see slow to you now - but once the skill is learned, it is LEARNED. Baked safely into your physical memory, a cooperative neural relationship between your concious mind, and your muscle-memory in your hands.

Just imagine if you were trying to learn to tie your shoes at this point in your life, for the first time ever. It too would take slow repetition, but ulitmately, you'd be able to whip right through the whole operation without a thought.