Normally more ball speed or move your target further down the lane.
Hand wise,add more rotation. If your fingers wind up at 90 degrees, that maximizes the rotation BUT it will also add backend, unless you add more ball speed.
More tricky is to add more tilt, but will change your PAP,most of the time, and change the ball reaction a little besides adding length. Since you're asking this question, I wouldn't try this.
Other options are to move deeper to catch more midlane oil. It and increased ball speed are possibly to 2 more useful options to get more length. Of course, you could change ball if you're not somewhat skilled in the above. If you were, then you wouldn't be asking this question ...
"None are so blind as those who will not see."