I'm a flusher myself. I flush with 1-2 times the volume of planter. Then water as normal. Flushing good lets you use your nutes a little longer. I flush 7-10 days before harvest, but with a good flushing, with a agent, I've read some growers have used nutes, to 3-4 days before a harvest. I flush every few weeks, all the time though, just not at harvest. I don't like the salts/nutes build up and the plants dig all water bringing that oxygen. It can't hurt...
Flushing at least once a month, koolkat