I have a towel bar in the bathroom that fell off the wall because of deteriorating drywall. What is the proper way to repair the hole? It is approximately one inch long and 1/2 inch wide. The towel bar has a mounting bracket that is held in by two screws. When I tried to fill the hole with joint compound and redrill the small holes for the screws, the compound just flaked away back into the wall void. Any help would be greatly appreciated.