An important skill necessary for dive bombing, that is seldom ever mentioned, is judging the required "overshoot" before releasing the bomb. Because the bomb will follow a parabolic (more or less) trajectory and will fall, due to gravity, off the tangent of flight. Because of this, aiming directly at the target will cause the bomb to fall "short". (Only in a 90-degree dive will the bomb fall on the aircraft's trajectory tangent.) Thus, at some point before releasing the bomb, the target will have to be "under the nose" of the aircraft and out of sight. The amount of overshoot required is a learned skill based on wind direction, aircraft velocity, distance to target, etc. The pics are from the manual for an ASG-10 "toss bombing" sight developed late in the war. A copy is on this site.