Flushing! No idea how to do it...

So my girl is in week 3 of flowering, and I'm thinking I should flush it sometime soon. So for DWC, what is correct procedure? Drain, clean the inside of reservoir, and then what? How long should I let the roots sit in flush solution before replacing it with nutrient solution again? I think if I do this after week 3, and again after week 6, and then again for all of week 9 I should see improvements.

some pics for ya...

first pic is 5 days old and she's grown a good 6 inches since then, 2nd pic is from yesterday, one of the lower branches.

ba ba bada bump

what flush solution are you using?

empty your container and fill with just water for 2-3 days and then go back to your nutes!!

thanks,
just water? then whats the point of flora kleen?

I usually do that towards the end.

yeah, those flushing nutrients are used for the "final" flush before harvest

I'm almost at end of week 2 of 12/12 light cycle. Is it a necessity to flush her even before the "final" flush?