'Be sure and get the Zap stripper. I agree that 1000 would be a good place to start--again--use wet and dry--keep wetting it, so it does not clog up. The 320 was the maximum which I would use--if you are not familiar with wet sanding a hull, the 1000 would be in line.
There are "systems" for maintaining the gel coat/wax etc. I think it is best to stay with one system: Chemical Guys, 3 M, McGuires, Prestra, Marine 31, Collinite, West Marine, Smoove, StarBrite, Total Boat, Nautical one, and a half a dozen more. Stick with one system. A word of caution; Polyglow is similar to the Mop and Glow, if you have finally taken off a layer of the yellowing agent...not sure if you want to go back with it again. It looks great when you do it.
Now many are using "Silicone dioxide" (SiO2) is a ceramic coating such as Glide Coat, Ceramic spray, There are several different types of products--a water based solution sprayed on. The more expensive, and more difficult to apply material are organic solvent based, and professionally applied. All of these require careful surface preparation. My SUV has a ceramic coating, and is garage kept--so I will get a number of years of service. I also put some of the water based and small areas of the professional grade on both the hull of the last C Dory25 I owned and on my RV. This is amazing stuff! Some applications run more than $3,000 (for a C Dory sized boat).