Short answer to your questions. Without using specific product names, everybody has their own preference, if the GELCOAT is heavily oxidized you will need to use a very coarse buffing compound possibly wet sanding before the buffing. Work your way from coarse to fine compound and finish with a good quality marine wax. The hard part you will have to deal with is if you have a mix of PAINT and GELCOAT, you will buff thru the paint very easily, where the gelcoat is more forgiving. As far as preferences, I have used orange rouge (sp?) followed by white rouge, followed with a paste compound to fine polish, and followed with a good quality paste wax. Where you start depends on how bad the oxidation is. I have had great results with 3M products and Meguires products. Also be careful around any decals, if possible you will have better overall results removing the decals and replacing when done. You can tape over the decals with masking tape to protect, but you can't get too close as it will peel also.