Both the prize and the damage counters are part of the Power. Therefore, nothing and nothing. When you play the spray, you stop all effects of the Power, not just the parts positive to your opponent or anything like that. Of course, they can't use that Power on that Pokemon again on that turn unless it says "As many times during your turn." The same applies to Alakazam's Power Cancel, etc. Hope this helps a bit.
EDIT: It says on the card, "Prevent all effects of that Power." Just backing my point up.