Why would you do this? Bring more stress and friction on pads and rotors with 2 tons of weight? If its a rock, your going to cause more damage to your rotors.
Take off your tire and inspect the brake pad through the outlet that is provided.
It is relatively that simple.
He would do it to clean off the rotor surface. The brake rotor surface is bare cast iron and as such flash rusts really quickly with any significant moisture in the air. Especially if the cars sits outside over a few nights. This can cause all sorts of noise. Getting some speed and hitting the brake decently hard will clean the corrosion off the face of the rotor and quiet things down most of them time but it might take more than one stop.
Now, if it's a pebble that's stuck in his brakes, it's not going to get between the pads and the rotor since the pads sit right up against the rotor surface (not actively pressing on it) when they brakes are not applied. There is no room for a pebble to get in there. When I've seen pebbles get into brakes, they typically get wedged between the medal splash shield on the back side of the brake rotor and the rotor itself. Applying the brakes won't do anything to a pebble that is stuck in there. It also won't "damage" the rotor in any significant manner, it will just make a bunch of noise until you either remove it, or the rotor wears it down and it falls out. You might see a small scoring on the back of the rotor if you looked at it, but that will quickly wear away as the brakes are used. Remember, it's not just the pads that wear with then brakes are applied, the rotor wears too (at a far slower rate).
OP should definitely get a couple higher speed stops under his belt to see if the noise goes away. Corrosion is most likely the issue since the car sat outside for multiple nights.