By using baby boss rexes, a 150 lvl Carcharodontosaurus only needs one and the bar is instant full for you to ride. We killed the baby it with a lightning wyvern and just dragged it to the Carcha. He was happy and it was way quicker than killing wild dinos to drag. Do not trap it since there is a "bug" that can prevent them from taking the snack from you until they are set free again.

More Carcharodontosaurus Taming & KO Tips