A couple people have suggested you read MaineSail's information on putting a shine on topsides. I'll be at least the third to point it out to you. It's pretty much the gold standard for gelcoat. You can take snippets of advice from a variety of posts, and wonder why the end result isn't what you want, or use MaineSail's techniques.
The torn rotator cuff throws a bit of a wrench into the whole thing, though. Under no circumstance would I have used a powered sander, even with something as fine as 800 grit. Would have cleaned it first with an acid wash of Mary Kate On Off.
Yeah, I played around a lot with fiberglass in the past, and was able to get it from dull to sort of shiny. I've used MaineSail's methods to the letter on a couple boats now. BIG difference. The first was started with 600 and finer grits, compound and polish, until it looked like new. My current boat, a 1996, went from compounding to polish with no wet sanding (didn't need it), and now looks like new...gleams. Done correctly, as MaineSail points out, you'll have all your shine when you're done polishing. The wax doesn't really make much of a change. Just protects it. That's shine.
Given the state of your shoulder, you probably could have just done the acid wash, the Poli Glow wash, and applied the Poli Glow and called it good, and gotten a decent shine until you can do the entire process.