I never use bleach. Bleach is over-rated and is too caustic for the fabric. I use Mr. Clean or Liquid Spic and Span. I apply it to the underside with one of those Windex Outdoor window spray bottles that hook to a garden hose. Apply it, then use a cheap old sponge floor mop to wipe the cleaner around to take the black spots off. Yes, you're going to get wet, but it won't be bleach dripping on you. Then rinse it down with the rinse feature. Do the top the same way. You have to let it dry completely before stowing it, or you've just wasted your time. Also, tree saps will come off with GOOF-OFF.
'07 K3500 Silverado LT Crew Duramax (LBZ)
2016 Salem 27RKSS
1984 CHEV SCOTTSDALE K20 2GCGK24J0E1XXXXXX (Chevrolet Legends-Class of 2019)
"...exhaust fluid? We don't need no stinkin' exhaust fluid"