Can be guys learning from the ladies or vice versa.
For me, it was a (then) young, cute, sandy-haired, snaggle-toothed provider in Dallas 7 years ago who askd me to lick suuuuper slow. Like 10 seconds for one up-lick, starting from the taint. Yowza that got the juices flowing. I looked up and she was blushing and I knew I'd be keeping the technique. The reactions I've gotten from that have been unforgettable. It's not to every woman's taste, but most like it a little and some like it a lot. I've felt the energy go from "random people in a transaction" to "horny fast friends" in two loooong licks.