No suggestions for you, as I've never really had a dog that humped..most of my dogs have been female.

However..I wanted to say that Delilah on occasion humps my dad's male pomeranian's face. It is HYSTERICAL. I know I shouldn't laugh..but oh my god is it funny. She'll do it for like 5 seconds and then be done. I've only seen her do it a few times haha. She has the ends confused..and gender roles..