All of the above have some good suggestions. I used to use pure ivory flakes, with a little bleach. Also the Woolite. I have always hand washed the covers, but some do feel that the machine washing is fine.
Today we have the 303 fabric cleaner, and that is what I use. I also do use dilute bleach, to get rid of any residual mold.
After cleaning and drying, I then spray with 303 fabric protector.
I was told a couple of weeks ago that Sunbrella now is made in China. My source is a very reliable person, and for the use I wanted he suggested Stattler marine fabric. This is made in Austria, and he felt that both the weave and the material was now superior for Sunbrella.
The only issue I would be concerned about with in browntdb's case is the taking "Those covers that had been stapled to their bases and reversed the fabric and snipped off all the loose ends that protruded from the seams." Was there piping around the seams? I would be concerned that the fabric was just single or even double sewn, and the edges may begin to pull out.
Let us know how this works out.