The reason you can't sell the resources ( the option is grey not white ) is because you already have max money. There's a limit on how much money you can earn for example if you have max money activated 124450652 what ever the number is it will reset to 500000 as that's the max GMP you can have in turn you can't sell items if your at the max limit.. Max resources work a charm. But that's the only reason I can think you were having that issue above. Just have the option turned on you will be eventually able to sell what ever you want once you spend some money on guns etc.. Then your resources will go to max 3000.
Place the files in your MGS Trainer Folder... Run the Trainer_Launcher.xex file. Console will reboot to FSD main menu.. Then launch your Default.xex file in your game folder "MGS V: TPP Game" and press DPAD UP + Back. It works.