I use West Marine brand Hvy Duty Cleaner on the non skid for periodic deep cleanings. For monthly wash downs, I use West Marine Brand Boat Soap ( the pink stuff) . The pink boat soap doesn’t remove all the Woody Wax From the nonskid, and does a decent job of cleaning. That’s what several of the boat detailing companies who wash boats use. I hose off the boat thoroughly after every use, especially all the hardware. (We sail in salt water)
I buy the West Marine products during their annual BOGO sale, so the price is very reasonable. $30-$40 worth lasts me through 15-18 months of use. We sail year round.
For really tough yellowing and stains, I carefully apply MaryKote On & Off Gel, which is a very strong acid. Don’t get it on metal! I use it at the waterline too, for waterline stains. Don’t get it on bottom paint.
for rust stains on stainless and in gelcoat, I use Spotless Stainless, a citrus based passivating cleaner. The trick to that is to use it when it’s 70 F or warmer. Otherwise you have to do multiple applications and wait a long time.
I don’t use any abrasive products on the gelcoat, even Barkeepers Friend or Clorox Softscub. Too abrasive.