I hand raised a weak kitten, not able to nurse well.  My vet recommended
using goat's milk.  Said it was well tolerated be young kittens and mine did
very well onit.  As someone else remarked you do have to make sure you're
feeding often and stimulate the anus to eliminate.  I used a warm moist
cloth.  I just used it straight from the carton, warmed to room temp.  I
tried the kitten milk repacer, I don't think it worked any better and it was
a lot more expensive.

Just my .02 worth.

Linda Mosher, LLLL kalamazoo MI