Dani Busboom Kelly, Head Coach at the University of Louisville, has a special tool for her liberos and defenders: what she calls a "setter board."
Set the board up in the right back position, where the setter would normally be releasing from. One player or coach hits driven balls at the board. One at a time, defenders (liberos or passers) from left back release and set the ball that bounces off of the board.
Also, have your liberos practice the "two shoot" shot. Instead of setting the ball after it bounces off of the board, the libero can fake a set and then shoot the ball sideways to the other side. Though this is a shot that should be used sparingly and only in emergency situations, once in a while the shot will catch the opposing team off-guard and score a point.
