I read an article about this sport once. The reporter is gay and I think English, not American. They asked him to participate in which he did. They are drenched in oil and the grapple begins. According to the reporter his opponent reached down his trunks grabbed him and proceeded to give him a HJ all the way to climax all the while the reporter had one of his hands down the backside of the opponent and proceeded to do some exploring.
Though the referee's are looking for just this type of action in order to disqualify wrestlers, it's often difficult to see down ones pants. Part of the rules are No ball grabbing and no anal probing. The real reason they reach down each others pants is to try and get some leverage on the slippery opponent.