If it's necessary for the man to slow down to avoid ejaculating, but the woman is close to orgasm and doesn't want thrusting to stop, there are a few options. Obviously, the man can stop thrusting and massage the clitoris or vagina with his hand. This movement is driven by the pelvis, and can be a lot of fun. Gravity assists in ejaculatory control, and because the man can relax his pelvic muscles it's MUCH easier for him to pay attention to what's going on and slow things down if ejaculation is too close. This position also allows the woman to stimulate her clitoris during sex.
Clitoral stimulation is easy, and G-spot stimulation is pretty direct.
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