That's the challenge with boat (and car) details, many times, a single step just won't make much of a difference. Multi step processes are time consuming and expensive but there is only so much you can do with a single step since you won't be able to go over it again. You can only use a fairly fine polish instead of a more aggressive pad and compound necessary to take out scratches, oxidation and other contaminants.
I'm about half done with my older truck, it's taking 3 steps to get the paint to look like someone actually did something other than a wash. One aggressive, second was lighter pressure and third with a lighter pad and compound to take the previous pass marks out. Fourth step is the coating. That's after a thorough wash, iron remover, clay bar and another wash, so 7-8 steps in total.
Unfortunately, there aren't any shortcuts. Single steps are only good for surfaces already in good to great shape and will only take out the most minor swirls, very shallow scratches and shine it up a bit. It's not going to be a big difference unless you have a dark finish that is really swirly or has quite a few very shallow scratches.
Most buyers aren't going to look that close at the finish, sounds like you got enough done to make a difference and get it in someone else's driveway.
