That is a query that some of us have been following ever since fiberglass boats were first publicly sold- (I owned a 1940 "Wizard", which I painted with Monoepoxy)
Here is a link to a older but still valid series of responses to a post in The Hull Truth
I"ll warn you it is lengthy. Probably take a full evening to review. But so is the job of restoring boats' gel coats.
I usually wash the boat regularly using a Blue Coral soap/wax. If there are areas which need any compounding, then I will use a wool pad on a non orbital buffer/compunder. I am recently trying the one from Northern Tools, which is a grade up from Harbor Freight (I think--because it will continue to hold its speed like the Makita and Portor Cable will) I got a Makita backing plate and wool pads (better than what comes with it). (I loaned out my Porter Cable and it never came back!)
I have used various compounds thru the years. 3 M makes a number of very good products. " Finesse it " comes in several grits--the fine polish is very good. After any polish I wipe off with microfiber cloths. If a boat has scratches or very badly oxidized gel coat, you will start with 320 wet dry, 600, 1000, 1500, 2000 Wet and Dry (wet) and then 3000 3M pad, finally with a compound and then polish.
For just normal use, I use Colinite Fiberglass Boat cleaner. If I am feeling super ambitious, I use the paste Colinite Fleet Wax. If the prior wax job is still in good shape I use the McGuires Flagship marine wax. It is not as hard as the Colinite, but goes on a lot easier. It is wipe on let dry and wipe off. I. apply with either a pad for wax and wipe with microfiber cloths. Some times I use an older random orbital 6" with a foam pad if I am doing the entire hull. If I use the Colinite, then I have an 8" random orbital buffer with a very soft wool pad.
Recently I have been doing some experiments: Mckee's 37 has a full line of products and Have used their Hydro Blue Sio2 Coating. This is a prep the surface, get it wet and then spray on the liquid, wash it off. I used 6 different products on the black hull stripe of our 25 most recently before the Hontoon Gathering. The jury is still out, but the McKee's was not one of the top products. The best was Colinite Fleet wax. But I have also been using the Zep Floor High Traffic Floor Polish. It is probably a very similar formula to Poly Glow. I believe that the cabin top of my 25 had the Polyglow on it when I bought it, although the seller denied that. ( I have also tried NuFinish and similar products.)
There are boaters and detailers who claim that there is one best or easy way...I have not found it yet!