Long greenside bunker shots are a difficult proposition.
You are faced with hitting over a lot of sand and the distance required for the shot can often be 30-40 yards. You need to approach this shot very positively and not get caught between two minds of whether to play the shot like a bunker shot and take the sand or whether to play it like a gentle pitch and take the ball cleanly. Playing an aggressive bunker shot where you take the sand to explode the ball from the bunker is a very high risk proposition so take the approach of playing from this situation as you would to play a gentle pitch.
Play the shot with your pitching wedge or 9 iron depending upon the distance required and the bunker face. Hold lower down on the handle than usual to shorten the distance between yourself and the club head which will encourage a clean strike. Create a solid stance to play from but do not wriggle your feet into the sand too much as you do not want to lower yourself below the surface as this would result in you striking the sand and we want a clean strike with the club head connecting with the ball, not the sand.
Play the ball from the middle of your stance as this will encourage you to catch the ball slightly on your downswing, allowing you to strike the ball first rather than the sand and to play a clean shot. Make an easy swing and work on maintaining your height throughout your swing. Keep your head in position, your spine at the same angle and the flex in your knees the same throughout your backswing and downswing and this will prevent you from dropping your height which would produce a shot where the club head struck the sand before the ball.
Striking the sand before the ball will result in all of the club head speed being transferred from the club head into the sand rather than the ball and the ball will not travel far enough towards the target.
When you play the shot, play it with your ears. This means listen to the club head connecting with the golf ball and making a crisp click, rather than a splash as it connects with the sand.
As you hear this click between the golf ball and the club head, work on rotating your body through the shot and towards the target and achieve a high finish position to ensure the ball clears the bunker and reaches the target.