Are you sure that you need to wet sand everything. It takes a lot of time. A "good" heavy compound will take down a lot of oxidation and marking. Probably as important is to get a few good pads. I recently did my boat and the pad were @ $28 a piece, but there were noticeably better than the pads that came with the polisher.
If you do need to wet sand, start with the least abrasive that you can and work down if you need more. I would start at 1500, if you need to wet sand. Also, buy plenty of it because those fine grits clog quickly.
1997 PS 205