In all my years I've never had to resort to this. Doesn't mean it doesn't work though. If you have a re-occurring pasty butt problem, then what do you think is the root cause? As a one time thing, just gentle warm water should be enough for a baby chick. But what is going on.... ??
Good question! Pasty butt if relative to stress should be temporary. If not temporary then you know it's likely relative to heat. I brood on the cooler side, starting in the *80's not 90-100 and I've never had to deal with pasty butt. Instead I know what you're talking about with just a little...