I not only keep my Grady nicely polished, but I also restore 13 ft Whalers (#8 is in the garage). Most of them are in tough shape with oxidation inside and out. I have a Shurhold DA, Makita rotary, and a variable speed HF 7" rotary. After trying them all, I use the HF rotary 90% of the time because it has the power and, as mentioned above, the 7" pad saves time. It is heavy so that is a negative.
As Seasick mentioned, the key is the pads. For heavy oxidation I use a Lake Country wool pad and for less cutting, the Lake Country purple wool pads. They hold up really well but you do have to remove the accumulated compound/gelcoat from the pad periodically. At the end of the day, I wash them in the sink with Dawn, let them dry and they're as good as new.
I know some like the foam pads, but I've never had much luck with them.
WRT the compound, the 3M Imperial works really well but their Restorer & wax does a nice job as well. Keep the pad moving and do a 2x2ft area and it will come out nice.