I introduce my puppies to ground up dry food at around 3 1/2 to 4 weeks old, as soon as the puppies are able to start walking. I put Chicken Soup dry puppy food in a blender and grind it until it is very fine. I put this ground dry food in a bowl in the x-pen with the pups along with a bowl of water. The puppies will go over and start licking the dry food. As the puppies get older they will start eating more and more of the dry food and mom will slowly dry up. Usually by 8 to 10 weeks the pups are nursing very little. All my moms have always had plenty of milk so I never felt it was necessary to make the mush. Some breeder prefer to wean them on mush. Either method will work but I have found the dry food method works best for me and it is a lot less messy although the pups will manage to spill some of it. As the pups get older I grind the food less so they can start eating the whole kibble. I like to use those small double sided bowls they sell at Wal-mart. I will put dry food in both sides and I will just another small double sided bowl for the water.
In one of my last litters I had a 'digger'. As soon as I would fill the bowl with dry food he would run over and start digging in the food.
I guess he liked to eat off the floor.
I forgot to add that when the pups are around 6 weeks old I start adding a little canned Pedigree Lamb and Rice puppy food to the ground up dry food. I blend in the canned food with the dry food so it is just a little moist. I put a small plate full of this food out twice a day in addition to their dry food. My moms always eat some of the puppies food but I feed my moms in a separate area.