Use of salt with pp works well, better than pp alone. Ideally increase salt over several days to allow the fish to adjust to it. I have used salt up to 1% levels when battling some parasites.
i have not used salt for many years now, when I stopped buying new koi from several dealers each year, my problems with koi health quickly went away.
do not use high salt levels with formalin products, that can present problems, at high salt levels.