Never let the mama dog chew the cord herself. i place a hemostat about one and a half inches from the puppy on the cord and cut on the side next to the mama after I have pushed upwards toward the puppy on the cord to get the blood and whatever back to the puppy.. I don't tie off or use quick stop altho some people do. i leave the hemostats for a few seconds and there is no blood. I have tried in the past to put something on it but it makes the mama try to chew it or keep licking it. before I even worry about that tho, I clean the sac off the puppy, suction it's nose and mouth out and dry it vigorously with a clean wash cloth. this stimulates the breathing. i also do my own dew claws and tails. Hemostats, clamp and twist method on the tail and scissors on the claws. Here is where you can go to learn more than you will read in those books.
Dog Breeding and Canine Reproduction by Debbie Jensen. Dog Breeding and Whelping guide for dog breeders.. Good luck with your litter.