I am a pro masseur in Denver, and I got into giving prostate massage as a request from a couple of clients. (Yes, its massage, and yes, I give my clients a "happy ending.") I have actually gained a reputation about this! Thing of it is, guys... its totally safe if you are without any wounds, its a great experience because I can tell you its a different sensation from that of getting fucked. Its not as much an "in and out" sensation, but if you work the prostate right it is totally hot and erotic. I've brought guys off without even touching their cock. :-D
A few notes though... If there is a way, please clean out first. No, not just pass as usual, I mean get the hose and clean out. Its much more acceptable that way! Nothing like encountering stuff during play. Good systems (a "Y" adapter to the shower head, the flexhose, and a couple of nozzles) is usually about $60 or $70, but well worth the investment.
Place a pillow under his hips, maybe a double pillow. It'll make him more accessible.
If you are doing this for the first time, use lots of lube and take it slow and easy. Essentially, massage hole for a few, without intent to go in. Then just go in a little... a quarter inch only, and slowly increase the depth. But SLOW is the operative word. When you feel a clampdown, stop, back out just a little, let the muscle stop spasming. Then slowly proceed. I have NEVER had a guy object to pain. Once past the sphincter, still take it easy, and get your finger in as deep as you can. Don't stroke dick as you go in at first... jacking dick tightens us up. After you're relaxed, then you can.
If he's face up, go in "palm up" and the prostate is up from there, between your finger and his cock. I'd describe the prostate as a "triangle" of sorts, and the point is close to you, so the triangle is flat side up, point down. How gay! (Pink Triangle symbol. LOL.) There us a "trough" on either side, and working that up and down is awesome, as well as the point spot trough. It is most sensitive. Also massage the mass of the prostate, easy at first, with increased pressure if it feels good. Some guys say it feels a bit like simple "pressure" but most find it very pleasurable.
You can lightly stroke dick and this is where you'll start warming up. I do a variety of combinations, which keeps the joy up but not heading to climax yet. Tease him and you'll have him wrapped around your finger. Huh, that's what he wants too, huh? (You need to do this more often!!!) When he's getting close, you can get somewhat agressive, because it will be a very intense moment. I'll bet he shoots a massive load. You'll know... you feel the prostate tighten like crazy. Woof!
The intensity is such that you should NOT withdraw right away. Just slow down, stop. Hold his dick cuz it still feels great, though sensitive. When he comes back to earth, catches his breath, then SLOWLY withdraw. That dazed look in his eyes will tell you that he just went to another galaxy and may not be sure if you were there along with him, but he's back!
Bottom line is that there are more nerve endings in this area of the body than anywhere else. No wonder its pleasurable. Go with it guys. Safe fun like this is awesome. And when a bit more experienced with it, try two or more fingers.
For anyone wanting a demo, drop me a line. Yes, you have to be present to win. I'll do this massage on about anyone. Of course, I may be jacking off just after you unload... its a turnon to me too.
One final comment... I rather like the dynamic here of 100% give/100% receive. I'll get my attention later. Its a time of pure concentration in that receiver, and that is great. Go with it, then make him please you later!