Catalina used a nice thick gelcoat, with a bit of work it can look almost new again. Mainesail wrote about his method in 2009 (Here it is on Sailnet). The directions and products have been updated over the years but the method is the same.
A rotary polisher like this Makita is key. Dual action polishers don't work, they are for cars where the finish is much harder than gel coat. Wool polishing bonnets, Presta Gel Coat compound, then  Presta polish and finally Collinite 885 Fleetwax will make the boat shine.
The job isn't hard, I find a bit of zen working my way around the boat.  First I clean the hull with a bit of dawn detergent in warm water, tape off the bottom paint and then starting on the port bow or starboard stern use compound on a of 3 or 4 foot section. Start the buffer slow, then increase the speed to remove the compound. Wipe with a microfiber cloth and move to the next section. Moving to the right is easier with the rotation of the buffer.
A good ladder, platform or scaffold is important, if you are reaching up with the buffer your arms and back will have complaints. That makes the work misery. 
When the compound is complete (the hull will look much better) do the same routine with Presta Polish. I use painters tape marks to keep track of the sections as I work.
Last apply several coats of Fleetwax with some extra coats at the waterline. Wipe the wax on with a circular motion then buff it off with a microfiber right away - don't let it dry on the hull.
The first time is the hardest, especially if anyone ever used PoliGlow on the hull. Each season after that  is much easier. I can't say I look forward to the task but once started I settle in for a few days work and enjoy seeing the improvement section by section.