Me personally I don't use flushing products I just use plain water for the last 2 weeks. But most flushing products seem to only have a n.p.k value of like 0-0-1 or something like that. I find that you can get great smoke from flushing and not flushing I just do it since it cleans out my soil of nutes at harvest and it seems the leaves have enough stuff left over in them to keep the plant doing great I've grown with flushing and without and haven't noticed a difference in my opinion flushing just saves you two weeks of nutes.