Well, you might actually want to ride with him sometime. I'd be curious to see how he actually rides ... make some excuse that you are going his way any way. Don't be critical at first just observe. Sometimes people will learn by seeing what you do. I'm not saying this will work but it is your best bet if you really want to help him. I've had a some success this way, getting people to ride clear of the door zone for example. Be patient, discuss things you might agree on like routing, then drop hints like, you know it's ok to make a left turn from the left lane, I'll show you how it works. Like I say, it takes patience.