No clue about percentages. But, I learned that I could do it while masturbating alone 2 or 3 years ago. I'm more of a "trickler" than a "gusher". I'd given myself multiple orgasms (I'm greedy lol) and kept pushing myself to get just one more. Boy did I ever. For me personally, it is very intense. It leaves me exhausted, drained, and really thirsty for whatever reason lol. It is unlike either clitoral or g-spot orgasms for me... and seriously only occurs after I've already had multiples of both clitoral and g-spot o's. In fact, if I go for a while (a month or two) without at least one good session of squirting, I can honestly feel the buildup. Anyway...
As a result, I always try to go pee before sex "just in case". I'm paranoid that one of these days that "gotta pee" feeling might actually come out as pee if I don't go potty first! The ejaculate and urine are *definitely* two totally different substances. It is not an all the time thing, but when it does happen, it's pretty amazing
