I know I am in the minority but I stopped making "mush" a long time ago. It never really made sense to me. A wild dog regurgitates recently eaten food for her pups. It's more solid than liquid so why do modern dog breeders make a mostly liquid formula to try to wean pups on?
I feed mama dog in the whelping pen. She gets slightly moistened puppy kibble and for some meals I add cottage cheese, yogurt, and/or canned food. The pups will eventually show an interest in what she is doing and go over to investigate. This happens between 3-4 weeks of age. Some of them will just smell around while others try to taste the food. (Sometimes mama dog will regurgitate and the pups will eat it.) Within a couple of days, all of the pups will be attempting to eat the food and that is when I start feeding them solids. I take puppy kibble and put it in a small, shallow dish and add enough hot water to cover it. Then I put a lid on the dish and let it sit for 5-10 minutes. The kibble should then be very soft. Since the pups are already familiar with the smell and already know it is something to eat from watching mama, they dive right in. They never have any problems eating and they do so with gusto. From that point on, they get some meals of kibble and some meals nursing from mama dog, until she gets fed up with their teeth and doesn't want to feed them any more.