There is one important thing about word “flush”... People started to use this term for a final flower phase, when they wanted to lower nuts in their medium. This is done because of osmotic presure in the root zone, which can draw back some exces nuts out of your plant. Of course this technicaly low presure can not suck all bad stuff out of your buds, but it can prevent exces of P and K in your buds (which cause “metal” taste). In fact all of people who talk about flushing, use this in sense of leaching. Flushing is getting rid of water unsoluble salts and you need to use some special chemicals for it. Leaching is lowering of EC of your medium. So technicaly everybody who lowers his EC down in the end of flowering is “flushing” (in a wrong sense of meaning)...