Here is an easier solution I just discovered when I was at a dog food/supply trade show recently. The product is called "Grandma Lucy's" and the formula is "Artisan", which is a fully dehydrated diet. It is grainless, using potato as the carb source, which is very very digestable, even on the teeny tiny systems. I tried it as my weaning formula with my last litter, adding warm water and a tad of goat's milk (which you can find either fresh or canned at the the grocery store) and LOVED the results. It has the consistency of instant mashed potatoes and the pups devoured it. I started them at 3 weeks and slowly added kibble to the formula as they got older. By the time we hit 6 weeks the litter was fully weaned, eating puppy kibble only moistened with water. I happen to feed the Enhance Professional Athlete as my kibble ....
http://www.grandmalucys.com