Hey man, that plant is looking nuts. Ask any three of my friends what their flushing technique is, and you'll usually get three different answers. Some people just use straight R/O water for anywhere from a few days to a week, depending on how hard you were going with the ppm's throughout your grow and what nutrient line you were using. Others use a flushing agents, but those have generally been proven to just be extremely low ppm solutions so you're basically just paying money for a bunch of salts inside some R/O water. Personally I'd probably just do a plain water flush, maybe using a flushing agent if you've already got one lying around that you use for periodic flushes for salts. Give it about five days, aerator running the entire time, and then just chop chop chop.
