just my 2 cents:
Wrestlers can sometimes be vulnerable to getting triangled when they pass to side control. They like to put the arm in the middle of the opponents legs(maintain position), but if they aren't careful, their head can be pushed down thereby capturing what's needed for the triangle(arm and head). Have him change his bottom arm position to either behind his close thigh, or elbow in front of his far hip.
The guard: Wrestlers are taught never to have their shoulders on the ground(on their back = pin). Being comfortable on the back is paramount in jiu jitsu. Have em start on their back until they get over freaking out being on their back.
Strength: Wrestlers love to muscle out of instances, whereas in jiu jitsu there is a slow technical escape to almost everything(if not everything). Teach him the technical escape for a submission that you see he is powering out of. There is a time to power out of positions, but usually a slow, methodical way of escaping is good to perform. Then he'll have guys saying, "Damn, he's a beast and he's technical!"
Rick