You've probably got worn gel-coat, on which subject i am the proud possessor of a nationally recognized test yacht. (g) The bleach probably cleaned things up, btw-Soft Scrub seems to work the best, but now you've got a chalky porous surface. The chalkiness is due to the age of the gel-coat and it is oxidation. If rubbing compound won't shine it up, and it probably won't-but try, you'll have to sand with 400-800 wet/dry paper (use it wet!) to remove the oxidation. Once the chalky oxidation is removed you are still stuck with porous gel-coat which catches all manner of dirt and stain inducing substances. Your interest in the Kiwigrip is understandable, not the least though because it will seal the gel-coat. I'm about to experiment with Woody's deck wax, another non-skid wax.
Once clean, you have to seal it in some manner or other, else you'll be forever cleaning. CardiacPaul's experience with Poliglow on the deck should convince anyone that, while it sealed great and sure did shine, sailing while wearing ice-skates is not desirable!
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.