Flushing? I use to. And, it was a big deal since i had 30-40 plants in 15 gallon pots. That's a lot of water and shop-vac-ing it out.
I'm now following a very experienced growers recommendation. Feed until the last three weeks of your cycle. From there, water/hygrozyme/sweetener and let the residual nutes in the SOIL be used. He has the finest tasting buds, so i'm following his lead.
Good luck,
this is what I do also, feed up till the last 3 weeks, then water with only molasses to soak up all the leftovers in the soil. By the time the last couple days of the plants life rolls around, the leaves are getting pretty yellow. I'm told my stuff tastes pretty decent.