From my experience, the prostate isn't something erogenous like the penis or clit, rather it's more subtle when massaged, and tends to compliment whatever is going on with the penis. When the penis is being stimulated, massaging the prostate can make you cum sooner and harder, and definitely is worth exploring. I've read though, that some guys can cum from just prostate massage. If you want to find it, try using a dildo or wand in your butt, and stroke the anterior (toward your tummy) wall with an in and out stroke, mostly out, milking the gland. You may even be able to make some cum emerge without actually having an orgasm, and I guess a complete expulsion is what they guys who cum this way are having, and you don't even have to be hard to make things happen.