I doubt you need to flush. I have seedlings that sprouted around August 30th in FFOF/HF mixed with pumice. (perlite was all out) Seedlings are doing great and looking healthy. I haven't tried planting straight into FFOF but I don't see why you'd have an issue...
Love this thread!
I just started an OG Kush x Clear Skies Autoflower using a blend of FFOF, Sunshine Mix 4, and pumice. (Local stores were sold out of perlite). I just planted the seed straight to the pot yesterday.
For my first plant in the pics (bag seed from some fire I bought long...