i use this and mix it myself, spend an hour one day and fill up 50-100 plastic ziploc bags, put in enough for 5 gallons of water. Easy to store, and you'll have it ready and wont have to constantly explain the mixture to employees.
i use new again roof and deck cleaner,followed by new again tannin brightner. these products work very well i down stream them using a suds sucker injector from xxxxxxxxxx.call1-866-639-2444, tell them suds mckenzie sent you. we suck it from a 5gal pail with very few jobs requiring a pump sprayer. other contractors use and love it too.
If anyone decides to try downstreaming sodium hydroxide, just be really careful........you dont want to get it on yourself, vegetation, or any brass kickplates on doors (learned that one the hard way).
I apply all of my deck cleaners and brightners using a deckhand sprayer. In my opinion, it offers more control, and less hours on my p/w.