If you experience ground resonance, cut the throttles immediately, this makes the blades all go to the lead position, and helps quell the resonance immediately. If you then apply the rotor brake, the blades are also tossed forward and pinned there by the rotor deceleration, a very quick cure.
Nick, can you clarify something, during ASTAR B2 training a couple of years ago, upon landing we got into the start of ground resonance and the IP immediately picked the aircraft off the ground. Would chopping the throttle be the recommended technique?
Side note, the mech insisted that the oleos were fine, after several more incidents the aircraft ended up at a different base (scheduled to be relocated prior to the occurences). Their maintenance staff replaced the oleos and the problem was fixed.