Well, I personally don't believe in
only telling a dog "no" when it's reacting to
overwhelming and natural hormones. If it was humping a person, I would then say no and redirect to his acceptable "lover dog"
(or blanket) - but I don't think a flat out "no" is the answer for an unaltered dog, in my opinion. It's like forbidding a dog to ever bark, to my mind - that wouldn't be natural to the dog. Both my boys are neutered, however, they have a stuffed lover dog and that's fine with us
.
I think shock collars are cruel - and I wouldn't recommend using one.
Has he been evaluated for breeding, btw? That'd be important as well.
In any case, his hormones are natural - and if you're not ever going to fix him, then I'd find a method that allows him to deal w/ his urges, without it interfering w/ humans. Good luck!