Barkeepers friend is good stuff but expensive for the job. It also works well on brass.
For badly oxidised gelcoat best to use a compound intended to remove the oxidation. 3M has 3 grades of compound. The most abrasive is very gritty. Not sure if I'd use that on thin RV gelcoats. Maybe use the medium, then the fine. Finish off with a good sealer or wax such as Meguires Flagship. Without protection that hard earned shine will disappear in no time at all.
Boat: 32' 1996 Albin 32+2, single Cummins 315hp
40+ night per year overnighter
2007 Alpenlite 34RLR
2006 Chevy 3500 LT, CC,LB 6.6L Diesel
Ham Radio: VP9KL, IRLP node 7995