the most important thing you can do is always talk to him about it and express your opinions dont leave anything out, my ex wife pulled my fantasies out much like you did with your SO she bought me things but when i wanted more like makeup and other girly things she never told me she was uncomfortable about it all in turn causing a rift and the demise of our relationship........... on a lighter note im with a woman who im incredibly open with and in turn shes open with me she tells me im pretty when i dress she helps me with my clothes and makeup and makes me feel secure and not weird about it... so thats the most important thing to do is be honest and open.. it has already been said above that hes probably been dressing up for years which is very true and likely dont make him feel like an outcast about it, he might further suppress his feelings
