All these suggestions are really good. As for commuting, I would (and do) use MTB pedals and shoes.
Next time you go out spray your cleat and pedal down with some chain lube to free up the mechanisms a bit and give you a better feel.
Also, if subtle ankle movements aren't working for you, try hugely exaggerated movements to try to clip out (while on a trainer or leaning against a wall). Throw your leg out like you're six years old and gliding through a giant puddle. It will help get the motion down.