Usually you want to splash your ball and the sand out of a bunker, but when the ball is buried this will cause a skull, so in this situation you need to use your sand wedge to dig below the ball
Your impact should start right at the ball and the lowest point of the divot should be ahead of impact, use this bunker drill to practice impact to develop consistent shots
Hitting the ball fat tends to come from either falling backward on your backswing or overusing your hands and uncocking your wrists too early