I have to agree with most people. The buddy needs to take the refresher course. You need to understand that your C-card is only the begining. You need to know how to respond if something goes wrong, how to plan a dive, how to debrief, ect....
And yes if he cannot afford a refresher course how do you know his gear is in shape to handle the dive. As for the idea of both you doing some basic skill drills in shallow water with you watching, this is bad, bad, bad. With a refresher you are in the hands of a pro. He will know how to contain any issue that comes up. Just a question to you, if your buddy bolts to the surface do you know how to react, in the regulator recovery drill if your buddy cannot find it do you know how to intervine and still have a postive outcome in place of a body recovery drill. Please, please please have him take a refresher.