Training animals for sex is wrong. The act must be consensual and ideally initiated by the animal, you must never use any treats, peanut butter, commands, or training methods to make an animal have sex with you or anyone else.
The reasoning behind that is simple, you can teach a dog to let a vet take his blood or trim his nails, clean ears... a clearly unpleasant possibly painful procedure that the dog will endure because there will be a reward in the end.
Bringing this to sex would completely rob you of any valuable feedback and you may end up doing something against the dog's will unknowingly or even worse, knowingly and the dog will withstand that for the reward.
Do not teach animals to have sex with people.