question about flushing

as i approch week 4 of flowering and the buds are getting bigger by the day i have a few questions.

my plants are in 5 gal buckets so i know when i do my preharvest flush i will use 10 gal to flush them.

i am going for optimum smoothness for smoking but i used chemical ferts the whole time. IE (24-7- and (10-30-10)

do i need to flush more then the preharvest flush? or am i ok with just 1 large flush at the end.

i don't have any nute burn

and help would be great

Just water with ph'd water the last 2-3 weeks, flushing get the nutes and salts out of the soil but the nutes are still in the plant so feeding the plant with just water will help with getting the nutes out of the plant and it will help with the smoothness and taste.