I discovered two things that helped.

1) Keep the weight off the hands. Grip the bar or hood lightly with almost no weight on the hands.

2) Keep the wrist in a neutral position. Check the arm, wrist and hand position, if the hand is not straight with the arm (back of hand to arm), the angle on the wrist creates pressure on the nerves and reduces blood flow, this create numbness in the hand and fingers. Try moving the fingers or rolling the hand around the bar or hoods to keep this angle straight as much as possible.

If I feel numbness, it's because I got lazy and find the arm to hand angle is bent. At least this has helped me. This is just good ergonomics, which should help reduce pressure points.

good luck