Who it's for, and when
Who it's for: any woman curious about her inner sensations, alone or with a partner, and partners who want to learn the move. No special flexibility needed: what it takes above all is patience and talking.
When: never from a cold start, always after long caresses, ideally just after a first orgasm or as she gets close to one. Pick a time free of tiredness and ticking clocks: in the morning, the body is rested, whereas late at night, if she's exhausted, it's better to rest a little first.
No pressure: not every woman has a sensitive G-spot, and the subject is still debated. If the area does nothing for her, that's neither a failure nor something missing: the exploration has no goal other than her pleasure, and the G-spot remains one caress among many.
Precautions: a sharp sensation at first contact is part of the game, but pain that persists deserves a doctor's or a sex therapist's opinion. The same goes for recurrent urinary infections, pregnancy or limited mobility (there are several ways to settle in: kneeling, on your back with legs raised, sitting, squatting or face down). Peeing after sex helps flush out bacteria, and fingers that have touched the anus get washed before going back to the vagina.