That depends, if your nutes are premixed into the soil, then flushing will further the problem (has been my experience, as it opens more morsels of ferts, thus fertilizing more). If you are adding the nutes yourself and the soil was nutritionally void before, then yes, flush the fuck out of it... 2-3 times the capacity of the bucket is the general rule. If you have a 5 gallon bucket, flush with 10 gallons of water atleast.. it's laborious too, but make sure not to let the water go down the sides of the pot, allow it to absorb into the middle, then come back and add more and more, tallying the jug everytime you've emptied it into the pot (to keep count). Let us know how it goes