Occasionally, you see hospitals welcoming husbands and boyfriends into their breast self-examination classes. The idea is that perhaps the woman is more likely to get her breast examined if her partner is doing it. The same goes here. It's not difficult to teach your partner how to examine your prostate gland. Aesthetics aside, this is something every individual couple has to decide if they want to do.
Many men can tell when their prostate is being touched because it's very sensitive.
If you're having someone else do it, you'll know immediately when they reach paydirt. If you're doing it yourself, it will also be obvious. Most folks are surprised by how deep they have to reach. You'd have to have long fingers, indeed, to reach completely to the far end of the prostate gland, but in medicine we are content to touch as much of the surface as possible. As with breast self-examination, you want to cover all surfaces, and you should be consistent in how you approach it.