It is with humility that I even presume to add to Exon's thoughts on this topic, since he is the Zen Master of prostate massages. Some of the girls who are good at this actually put a small condom on the finger they are going to use. All I can tell you is that having your prostate massaged while simultaneously having Mozart's 5th Symphony for skin flute played on Mr. Lucky, is as good as life gets.
Go for it Big Guy and enjoy.