When hook and string keeps failing and difficult areas to reach abound - try two small bar magnets (shown as batteries) that will attract to each other.
Vertical line is bar magnet on long string and lower horizontal line is stiff wire with bar magnet on end to move into range of vertical bar magnet. After magnets connect slowly play out more string until wire and string comes out of wall opening. Tie on wire to string to feed and pull wire into wall.
