I do exactly what Evan describes except I think of it as centimeters for some reason. the flipper is 7 or 8 cm's long. "This ramp is 1 cm from the end of the right flipper from a cradle or slow inlane roll." the backhand is 1 cm down the flipper.

The key to this technique is to trap up so that speed of roll down the flipper is slow and doesn't introduce another variable.

aiming well on the fly- there's no substitute for practice and experience there. Although you can apply rational thought and understanding of physics to help with that a little.