After touching down on the remote rough gravel airstrip, the pilot applied what he described as "hard braking" with the non-differential handbrake, while attempting to maintain directional control with the nose wheel steering. As the pilot continued the landing roll, the airplane began to skid/slip off to the left side of the convex shaped runway crown, and it eventually exited the runway and impacted a large rock pile. After hitting the rock pile, the airplane nosed over onto its back, resulting in damage to the wings, and the rudder separating from its hinges.