Q: Some puppy kindergarten trainers use a squirt bottle to squirt water (with or without additives such as lemon juice, vinegar, Bitter Apple, etc.) to squirt a puppy if it plays too roughly with others. Do you consider this a positive and up-to-date technique? Is this a technique you personally use or endorse? And if not, what would you recommend doing instead, when one pup in class plays too roughly with another?
A: This is punishment. I don't care for it. It is certainly not positive and it is not up-to-date. I don't think the puppy associates being sprayed with its own behavior; it might well blame the other puppy. Also other puppies might get sprayed by accident.
About ten years ago I wrote a piece on the web about spraying my dog (once, only) to establish the scent of vanilla as a conditioned aversive. I then sprayed the wastebaskets to keep her from raiding them and tearing up used Kleenexes. Worked great. Catching her and spraying her as she dove into the wastebaskets would not have worked at all (which is what people are doing when they spray puppies at play). However there may be an impression out there still, somewhere, that Karen Pryor uses nasty spray bottles so it must be okay.
So, no I don't use this or endorse it.
If a puppy gets "too rough," remove it and crate it for a few minutes. Or put it with larger or older companions to learn some dog manners.