Of he hundred or so boats that i ahve done this year, that one looks pretty bad. Red gelcoat is deinatly the worst, followed clsly by blue and black. It just qxidizes fast and deep. The tru best fix for that is a wool cutting pad, or even a foam cuting pad, with 3M Super Duty compound. Work it fast and pretty hot, and you will be left with an amazing surface. I typically will follow that straight up with 3m's light cut cleaner wax on a rotary with a cuting pad, foam. that leaves he surface pretty shined and protected. any spots that you cant get of by machine, try using "Roll Off" It will work wonders. In fact i would wash the whole boat with it first inorder to get the oxidation loosened up and thinned out.
If you want a real good outline on how to do it, PM me your phone number, and i will give you a call, and spit out as many pointers as i can. Boats are a whole different world, and must be treated as such!
good luck
Mike