I've only experienced pompoir or the singapore kiss once - with the legendary Kavita. Kavita had the ability "to “suck the penis” into the vagina, the expel ability similarly allows them to push it out. Then there’s the lock ability, where females clench down on the penis to hold it in place."
It was an amazing technique and one i hope other WG's would practice:
www.alternet.org/ancient-largely-forgotten-technique-women-can-do-give-supergasms