Most Helpful Guys
You'll need to indicate to him more obviously and more intensely that you want him to approach are approachable/friendly, and even then you'll usually get better results by approaching him first with a big smile on your face and asking him how he is doing. Make sure he sees you looking at him and smiling- he needs to feel confident that he won't get rejected if he approaches and he will usually have to work up some courage to do it.
You can do the approaching. Ask for directions or have him explain some mechanical thing. Any excuse, just meet him. And, be sure to touch his arm at some point in the proceedings.
Most Helpful Girl
You should approach him if he's too shy to do it. I think it's pointless to wait until he gathers the courage. You'll probably wait a long time... or eternally.