Although you may have the feeling your arm swing is too slow, there is never an instance where the arm swing is a limiting factor in the speed of the leg swing. There is actually a pause at both the extreme forward and extreme back positions of the arm swing so that the legs can catch up to the arm swing. This is observable in all runners at all speeds. So keeping this in mind there isn't much need to do "speed training" for the arms. Having said that there isn't anything wrong with doing it and high intensity medicine ball work would probably be the best way to go if you were interested.