That's not really a flush at all but tapering down on feed is a good idea.
Are lower leaves beginning to yellow? If not make sure to use as little N as possible in the last bit of feeding. Too much N inhibits flowering in the later stages so it's better to have the plant steal it from the older leaves so it's getting just as much as it needs and no more.
I never flush but taper back to lower ppm in DWC and just low level feeding near the end in potted plants with just RO water the last week or so as there is always residual nutes left in the pots.