Some naturally retain it after their mother weans them. If you get a puppy right after weaning (6 to 8 weeks, the darker and older the better) you have a chance to rekindle that instinct and maybe keep it going. Don't forget the reason mom weans her pups, that is needle-sharp puppy teeth. You would have to be insane to offer your member to a chew-everything-with-those-new-teeth puppy, so I would suggest a bottle with an appropriate sized nipple, and regular feedings, and increase the size of the nipple to match their growth (feed supply store).
If you can get them to settle down and not chew it, you might consider introducing your parts flavored with milk. I wouldn't recommend cow's milk btw, a puppy replacement formula would be better, or goat's milk.
I've not done this and likely never will, but I have heard of others who were successful. I was fortunate enough to have met a few naturals over the years, but it is indeed a rare talent.