You can start weaning onto complete from 3 weeks, if you plan to feed complete. No need for anything else at all. Just soak until soft in hot water, then blend, gradually making it thicker/drier as pups get older.

I've never given lactol/puppy milk and never had a pup with the runs, which s is something lots of people sem to think is normal. The whole point of weaning is to get pups off milk, so feeding milk seems slightly odd to me, unles there is a specific reason for doing so.