in terms of opening up the clubface in playing a bunker shot, it depends how far i have to hit it.

if i only need to hit it 5 - 10m. i might open it up the face, stand 30degrees to the target and swing through the ball impacting about 1 - 2" behind the ball so i get a nice high loft out of the sand and stops almost dead.

if you open up teh face too much and hit too far your going to get way too much side spin, account for this by aiming left of the target 4 - 6ft.

if it's a longer shot 10 - 20m, play the ball like u would normally (ball maybe a tad forward in your stance) and hit just before the ball.

for the longer one again 50m+ i always try and hit the ball thin. you can generally control the speed at which u hit the ball and account for the ball flying quickly out of the bunker.