I believe the Clearex is only for a short period flush (15-60 minutes). That's what their website said anyway
As I understand the theory,the final flush is to remove the chemicals and elements that accumulated by adverse selection and/or from compounding.
Essentially, the leftovers that were either held in reserve by the plant for later use, or that were provided to the plant in excess quantity that the plant didn't spend the energy to dispose of, or the salts and such that remain behind.
So if your clearex step aides in unlocking, and there are no new nutes present to be used, the plant turns on itself and consumes those stores that's it's held in reserve.
I hope others jump in here because I qualify I'm offering opinions that I've formed from research; I'm sure there are people here far more experienced that I that can confirm or correct my comments.
That said, I think the choice you face is to starve your plants those last 4-7 days (DWC with nothing but pure water), which will surely help ensure that any residual nutrients that might remain are fully minimized, or add a carbo type product like bud candy or sweet leaf to provide an easily digestible non-chemical energy supply during the last phase on the plants life.
Like everything in life it's a tradeoff. With pure water, you'll more easily rid the built up nutrients but might not maximize swell. With carb supplements you'll maximize swelling but might not get rid of the last few points of residuals.
Soniq, thanks again! Your research on flushing coincides with mine and the 15-60 minutes does sound about right, especially when considering the first post of this thread.