I find that most guys my age are repulsed by the idea. meanwhile I wouldn't mind doing it to them. That is if I'm in a trusting relationship... cause I think anything that has to do with the ass is a pretty intimate :P.
yes, my boyfriend loves it, at first he was kinda freaked out by it, but its nothing to be ashamed of. have her use a finger with lots of lube, or you can use a small plug, made for male gspot stimulation, tantric sex books also have info if you are interested
Can't really attest to the increase in fluid, but there is certainly an increase in pleasure. Just insert your finger in the anus reaching forward towards the penis. About and inch and a half to two inches in you should feel a pea sized gland; that would be the prostate. Massage away!