There have been numerious studies out at one time, that a crying pup stimulates the milk "let down" sensation in the mother. ..
As far as care for the pup- make sure you wipe the back end with a warm cotton ball to stimulate the pup to go to the bathroom. The licking by the mother is the normal stimulation- and you are doing the same thing.
When is time to put the pup back with the group- the mother should NOT be present- remember- she will not recognize the returning pup as hers. ( she could see that pup as a threat to her pups.)