For what it's worth -
Our pup Bodhi is now 12 weeks old. When she was 8 weeks, she was on the skinny side, and the vet suggested we 'beef her up a bit'. She was on Hill's Science diet which was what she was getting at the SPCA.
Our vet suggested we use Medi-Cal development dry and canned for our pup, and then soak the kibble, and mix it with the canned food. So we got the bits we needed, and started to mix it with the science diet stuff to gradually change her over to Medi-Cal.
Well, first of all, after a day she got the trots. So we figured it would be the transition to this 'good' food she's now getting. We kept it up a bit. It didn't help that we had a major heat wave happening, so pup needed more water, was less physically active, etc. We couldn't see whether it was the weather or the food that was causing her stool to become thinner.
Anyway, after a month, we've concluded two things.
1) she gets the trots from the canned Medi-Cal.
2) she gets the trots from soaking her kibble. In fact, she won't eat soaked Medi-Cal development... no matter how long we leave it out for her, or whether it's breakfast, lunch or dinner.
3) she doesn't like the Science stuff soaked either - she'd prefer it dry, with water available at all times.
As long as we were giving her dry kibble, she'd have a solid stool. But she's still not 'beefed up', though she is growing very well.
We're currently changing to Orijen and we love how she's responding to that. Her stool is getting much better, rather than a compacted dry (almost crumbly but not constipated) stool, it's a nice thick paste. The colour is more consistent. It's coming out more consistently too - not in a dollop here, then waddle away, some more bits there...
While the Orijen brand isn't available in all pet stores, it is available in the ones that are closest to us, and it's even available in the local farmer's market. So it's not more 'out of the way' than only being able to get the food at the vet. It's easier for us, in fact. Another part of it is that we're wanting to go raw with the dog, but dh still wants to brush up on his research about it. Until he has, and until he feels comfortable with the information he finds, the Orijen dry food will be a much easier foundation for going raw than a grain-based or grain-containing kibble since both are biologically appropriate.