Here are some products that I use.
Woody Wax for decks and metals. Expensive but worth it. Flitz is also very good for metal.
303 Protectant. Good for vinyl and clear vinyl. I use it every fall before the storage of my cushions.
Starbrite water repellent. I used to use 303 Fabric but it is expensive if you want to treat large areas like Biminis, helm covers and the like, the Starbrite is a better deal. If I had new canvas, I probably would go back to 303 for several seasons.
Gary's wax. I have been using this for a decade or more. Maybe there are better waxes but it works for me so I stick with it.
Presta Finesse cream. A very light polish/compound. Good for rub marks.
Water line stains. Mary Kate On&Off. If I have options, I will but the less expensive options as long as they have oxalic acid in them. Note that hull cleaners are not friendly to galvanized trailers.
Black streaks. I haven't found a products that works really well for me. I usually end up just using a cleaner wax for light streaks or a mild polish for tougher ones.
Barnacles. After power washing and some scraping, the remaining pieces can be tough to remove. Muritic acid works very well but is also a dangerous material and probably banned at many marinas. The fumes can do serious damage. I probably shouldn't even have mentioned it. After reading up on barnacles, I am going to try a lime remover like CLR to see if it works.
Barkeepers Friend, the milder stuff ( says it's good for non stick pans)
With respect to diamond non skid decks, I have stated in the past and still believe that for some unknown reason, scrubbing with a cleanser and a rag works much better than the cleanser and a brush, soft or stiff. The trick with the rag is to scrub in one direction of the grooves and then scrub along the other direction of the grooves. For abrasive types of non skid, forget the rag, just brush.
I welcome others feedback