Instead of going for the waterworks skill shot, plunge the ball so it lands in the roll and collect saucer to advance the board.
Shooting Rail Road ramp 5x starts 2 ball MB. Easily backhanded from L flipper. Try holding flipper on return as ball may settle. Repeat.
If possible, start Cash Grab when multiball is lit; Cash Grab is the only mode in this game able to be stacked with multiball