Generally the mother will let you know when it's time to wean them. You might want to supplement that ground up food with some buttermilk or milk replacer for a few weeks. Just about any soft food will work well, but we nearly always put some milk or something in with it initially. Putting lard (wal mart sells it as "manteca") in the food helps as well. As soon as the mama shows you that it's time to wean, separate them. If you're feeding the smaller pups, we always feed AT LEAST twice a day, sometimes 3 times. It ain't all that hard, but remember every mama dog is a little different in how they go about weaning and at what age.