I pick up "Hi-Yield 38" (38%) in the 32oz at the local hardware for a little over $13.
At that price, I mix a small bucket, build a pile of dunkables and get to dunking. Clothes, hammocks, tarps, whole shebang gets dunked and hung out to dry in no time flat. Clothes get run through the wash once before wearing. My concentration is ussually "just a tad" over 1/2%.
I ussually have plenty skeeters hanging by one leg from the inside of the hammock netting when morning comes round. Works great for chiggers too!
Careful around the cats though. Stuff is extremely toxic to felines.