Nido is great stuff.  I mix it approximately half and half with Carnation instant dry milk to yield the 2% I'm used to.  It's true that Nido doesn't mix as quickly as Carnation, and it mixes better with hot water.  My approach is to use a 16-oz. Nalgene bottle (which I use for rehydrating other things as well) and mix the milk in the evening.  After sitting overnight it's just like out of the refrigerator, only usually not quite as cold.

Dave