Not a DP but received a double BJ once.
I have had many. They are wonderful and always surprising. I once had 20 internal orgasms in one session. I only stopped from pure exhaustion.
Humping a pillow on the bed looking at a Hustler magazine until I had my first ejaculation! I was soo shocked.
Would you masturbate in front of your wife or girlfriend? I have and do.
How about a stranger? I have.
How about another guy? I have.
Prostate orgasms are the strongest I have ever experienced.