The "scout" that Raiden mentions refers to a Native American warrior, and it has a different nuance from the terms "scout" or "patrol" commonly used by the army.
The basic idea has its roots in the attitude of Native Americans toward Nature; to understand Nature, to learn from Nature, to revere, love, and coexist with Nature. This attitude is said to be the bare essential of their way of life.
In fundamental terms, it is a philosophy based on "awareness." Tracking a prey would be an example of this philosophy. When pursuing an animal, the surroundings provide a hunter with indications as to the whereabouts of a quarry. Tracks, disturbances of leaves and branches, air movement, carry-overs (displaced objects that aren't native to an area or region); all these and more are clues that will lead a hunter to his or her prey.
By living with Nature form a very young age, Native Americans honed their awareness to the point that they can notice even the most minute details in their surroundings.
Using all five sense. Relying on the sensations of the skin. This is the art of the "scout" that Raiden mastered.