Pick the type of claw gouge that you want and set the matching bit into the rotary tool. A cut-off wheel will give a very thin gouge, while various grinding tips will give from an 1/8th inch to almost a 1/2 inch gouge. The inside of the gouge can be V-shaped as if a sharp claw made it, or more U-shaped from a dull claw.
Draw lines on the metal with a washable marker to represent the path of the gouges.
Put on your safety goggles.
Grip the rotary tool and turn it on. Carefully follow the path of the marker lines, applying pressure to the metal with the attachment tip. The greater the pressure the deeper the gouge will go into the metal.
Trace over the gouge again if the first attempt is not deep enough. Follow the same path exactly so that the claw marks look realistic.