I disagree with 600 being too aggressive, in fact it may not be aggressive enough to start depending on the condition of your gelcote. The gelcote is thicker than many think, particularly on boats of that age. The gelcote on 70's boats was never as highly polished as they come off the molds these days, so getting down to 1500 is completely unnecessary IMO. This is my boat on the day I picked her up. You can see how heavily oxidized it was. This was even more evident after removing the old name. It also had some deep scratches and gouges that could never be removed by starting with 600.
I started with 220 dry on a random orbit to work out all of the deep scratches, then moved on to 400 wet over the entire hull (on a previous boat the oxidation was so severe that I started with 220). Keep your paper wet the entire time and get a fresh sheet when it feels like it's no longer cutting. You will know when to change grit when a fresh sheet feels like it's no longer cutting. I've heard of people going all the way to 2000 grit but you really don't need to go past 800 to get fantastic results.
Here's what it looked like after wet sanding to 800 and then a scrub down with oxalic acid.
Your main objective is to get the color uniform with no blotchiness and no visible sanding marks. Unless you hate yourself, I'd forgo the compounding and waxing. Been down that road more times than I can count and I ain't going back. It looks great for a month and then the elbow grease starts all over again. I used Poli-Glow after all of the wet sanding and here is the result. The best part is I'm getting ready to start my 3rd season with it and it looks as good as it did the day I applied it.
