Building athletic glutes for sprinting (and looking good) isn't just about focusing on the gluteus maximus, but also the minimus and medius. Side walks and monster walks with a small band will really target these "forgotten" muscles.
For the side walks, think about tempo. Step out to the side quickly, but bring the other leg in slowly, really feeling the tension.
For monster walks, begin in the half squat position with your feet pulled apart as much as possible. After assuming this position, take small steps forward keeping your feet as far apart as possible. Perform 4 sets of 20 meters.
A lot of lifters think that hardgainers rank right up there with Big Foot and Nessie on the believability scale. Writer Phillip Nation begs to differ. He thinks that true hardgainers exist and, more importantly, can be cured.