Run over to one edge of the sound board, sound board more upright than normal almost perpendicular, run it at the end of the striker and use more pressure than normal. All of these make it higher pitched. I find it works better with slow speed across the striker with quite a bit of steady pressure. The quivery sound is tough. A little nervous vibration of the hand holding scratch box can do it but takes a lot of practice to get consistent. Some scratchers are Much better suited for this than others.
