You have just started a brand new unexpected market lol...they will catch up, haha!
Just a thought...in my small community, people are encouraged to place woodstove ash in a separate area/dumpster bin...kind of a recycling thing apparently...you might ask local waste management/government if...
IMHO DE is not necessary at all...others may have ideas about what to add but it is really pretty simple...mine will make dust baths in gardening beds if allowed and they fling the dirt everywhere, so high sides are recommended...fun to watch! Even baby chicks love dust baths:
first dust bath...
Nice! If you can put the ash in five gallon plastic buckets or totes you should have plenty for quite a while. Other additions for dust bath can be peat moss and/or top soil and/or dirt and/or sand....make up your own recipe. For my six, they sometimes dig their own dust baths but I used a tote...
Good plan! Wood ash...find a friend with a fireplace or wood stove?
Whitewash is part of your prevention going forward.
Keep coop as dry as possible...and consider a poop tray with sweet pdz that you empty daily of poop with a cat scoop. That will help with dry ness and good for bird health...
There is actually quite a current raging debate about the safety of borax but if it is worrisome, don't use it! While I usually am in complete agreement with LG, I will here respectfully disagree. I would use borax before bleach any day...
https://www.smallfootprintfamily.com/is-borax-toxic...
After you get everything to your liking (I think you have been given great advice), whitewashing the interior may help with prevention going forward.
Putting wood ash in the chickens' dustbath may also help...again going forward as a preventative...
I just wonder about their mite eggs...I am...