i always advise spraying as close to when pollen is going to drop as possible , its only a guess and sometimes you might spray a day or 2 longer then nessesary , but thats ok as typically the first male flowers seem to drop off instead of releasing pollen anyway
but yeah , i make my best bet i can and keep spraying until what i hope is maybe a couple days away from pollen being released
peace
edit, they are after all females , if we stop giving them silver we stop blocking the ethylene they naturally want to produce , and c.s. isnt potent like sts
some of my fully reversed plants end up finishing with female flowers on the bottom , but i usually kill them long before then , just saying , if given enough time they do start growing as girls again