Needs to gain confidence? There is a point where we eventually just sell out and start to stick a wheel in there. Sounds like he just needs to decide to do this or find another sport. This comes easier to some of us than others. I've known promising riders who could never really take this step.
Have a goal for his next race be to ride in the middle of traffic as much as possible. Doesn't matter how he finishes just so he is mixing it up the whole race.