Flairing a day prior won't do it. If it's just stress stripes do what was recommended to you. Just let him get used to his new home, no tapping on the tank, keep the lights dim, no changing him around. Add stress coat if you have it. He is brand new to you and his home, sometimes it takes a week or two before they relax.
I think that would be okay. Or you could take some water from his tank--just a cupful or so--and mix the conditioner with that and pour it back in. That way it wouldn't be just going in right in on top of him.