LOL, my mom was giving me flack for doing ENS, flipping the puppies all over the place, setting them on a cold, wet towel...
Poor little guys! I do feel bad doing it sometimes. So it got me to thinking about the timing of it. I do mine at night.
But I won't do it when their bellies are full bc I'm afraid they'll vomit. I won't do it while they're feeding for the same reason. I feel bad doing it when they're sleeping peacefully... And I feel bad doing it when they're waking up and getting ready to feed.
So typically, I'll do it when they're sleeping because they tend to be more relaxed.
Thankfully it doesn't take too much time to do it, just a few days left for me!