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
Hitting a guaranteed draw every time, to get around things like a tree, is simply learning how to set up for the shot with a closed clubface, closed stance, do not turn your body too early and allow your forearms to rotate through the shot more
Practice what a proper impact position should be lin the mirror and then go to the range and take small swings starting at your impact position