I'm not a pro detailer by any means, but doing cars is a hobby of mine for more years than I care to remember. Including getting them ready to show in some cases.
My experience with cars helps me do a pretty decent job on the tired old finish on my boat every spring. Some might say that it's as good as most pro detailers could do given the age of the finish, and a lot better than some.
There is no easy way to do a really good job.
The outcome will only be as good as the surface pprep.
For a quick, and very decent looking job with an easy to use all in one product you could try Garry's Cleaner Wax. I use it sometimes on spots during the season, and I see that a lot of "Detailers" and Marina's use it on their customers boats because it is a one step product that looks good fast. It has a heavy solvent content which cleans the surface pretty well and leaves a pretty nice shine. Open the jar, take a whiff, and you'll smell the solvent. Just don't ever put it anywhere near a car's much more delicate finish.
A better long term solution is to deep clean the finish with a polish (or compound if needed) to bring the shine up. Always go with the least aggressive polish first, before going to a compound. If the surface is not really bad, a good polish will do the job. If it is really bad or has a lot of surface scratches than it will need to be wet sanded. I would not try to wet sand if you have never done it before.
Think of compounds and polishes in terms of sanding a piece of wood with compound being the heavy grit, and polish being a finer grit. Today's compounds and polishes have diminishing abrasives in them that break down as you work it with a buffer. They leave very little, if any, residue when used with a rotary buffer.
The compound will do heavier work but take more from the surface, and the polish will do the lighter stuff and produce a deeper and smoother shine.
Real good, and lasting results will require a wool pad and decent Rotary buffer. I use a Makita 9227, but lots of guys do real well with the cheapo version from Harbor Freight. A rotary buffer is a great thing to have, and although you should never go near a car with one unless you know what you are doing, the gel-coat on a boat is a lot tougher and a good place to practice.
Don't waste your time or money on a random orbital type machine. I have a couple of high end ones I use on cars all the time and they are fantastic, but they are useless for real surface correction on the boat.
If you compound, then follow with polish. If you polish, then follow up with wax or sealant to protect the surface.
Lot's of people get confused and may think that polish and wax are the same thing because of the way some products are marketed. They are not really the same. A polish corrects the surface, and a wax protects it. While a true wax is generally a carnauba based product, sealants that are made up of synthetics are also used to protect these days. The sealants are usually a little longer lasting, but a lot of people think the carnauba based stuff gives a deeper shine.
If you use the Garry's, you will get better results using it with a rotary buffer and wool polishing pad. That's what most of the pro's do.
A lot of spots above the rub rails are tough to get at with a machine on most boats. But your boat sounds pretty big and you might be able to get to a lot of it with the rotary and just do the hard spots by hand.
Lot's of good products out there, but try to stick with stuff that is made for marine use. I have a couple of garage shelves full of stuff that I use on cars, but as great as it is for them it just doesn't hold up on boats.
