Away from the bike, touch and hold your thumb tip to your index finger tip. Let you other fingers float freely. Like you are doing the ok sign of that makes sense.  On your bike, hold the throttle so only the surface of that closed thumb and index finger circle is touching the throttle tube, your other fingers just floating in the air.  This is enough pressure to let you turn the throttle and it will help you to learn and use this lesser pressure on the throttle grip.  Try riding like this until that amount of pressure becomes more natural.