Weaning process starts around 4 weeks of age
Don't pull the moms out till pups are at least 7 weeks old!
Even though 4 week old pups can eat some food, we prefer to leave the mom in longer. There are many different thoughts on this, and I know we used to send pups home at 5-6 weeks of age thru the 70's 80's, & 90s before society deemed it "bad". I don't disagree with leaving in a little longer because it was hard for new owners who had no experience with babies, but remember not to let people who assign human emotions to animals dictate what is natural for the animal. In the wild, moms start weaning at 4 weeks because little teeth hurt and mom's will eventually nip at the pups and can hurt them.
Introduce a small bite solid food
I never offer mash. Instead get a tiny bite hard food. Don't wet it. Don't give them extra milk. Basically the same thing that mom should have been eating all along. Just be sure to use a pan the pups can eat out of. Wet food can sour, and even it doesn't make the pup sick it will attract pests.
Water
Pups can start drinking at this point. Be sure that the water bucket is something the pups can drink from, but not drown in. Also, water should always be the first thing in the front of the pen so you can see inside of the container at all times.