Your right he lacks the confidence. I think it's also who he is. He is professional but then a total party animal when out of work.
It took me weeks but he finally caved in an wore a total outfit for me. A tiny black corset, latex miniskirt, black g string and 7 inch heels.
It was funny I had to tie his corset, he looked rather cute all dressed up like that. He was hobbling around so I had to teach him how to walk in his heels. He complained but he was really good.
He's been talking about his thongs and says he feels ashamed of himself that I saw. I don't know how to suggest. But have some quite cute shots.