I can't comment on DrJ58's post concerning the use of using 2 fingers for palpation of what he was describing, not because he's wrong, but because I don't honestly know either way. If I had to render a guess, I would say he's probably correct in using 2 in the situation in which he is speaking.
I will say this though, using 2 fingers in a normal exam is actually a bad thing. It's sort of hard to explain. When doing a normal rectal check, one of the reasons to insert a finger back there is to feel the rectum walls. With one finger your brain can register what your one finger is feeling. With two fingers, your brain can't accurately feel or register what is being felt by both fingers at the same time. It's why sometimes in the old days the nurse would swat an injection site prior to darting the needle in. Your brain can't register both pain centers at once. Sometimes if I have to give a patient 2 shots, I administer them both at the same time. Using two fingers in a rectum you are unable to feel a 360 of the rectum.
As far as positioning of your fingers, I place one on top of the other, or my index finger crossed and below the middle finger until I get inside and then wait for both rings to relax then I uncross my fingers. This of course is in a play situation only. Also, no matter if I have him on his knees, or on his back, I always enter him with my palm facing his belly button that way your fingers are curving with his natural body curves too.
I hope this helps some too.