Milk it

You smile at her back. She'll get to cum alright.
You wrap your fingers around her shaft and begin pumping.
"Ah, what-- Oh, god, that feels amazing."
You tighten your grip and begin pumping faster. She moans again and again as you do.
"Oh, god, please, slow down just a little. It's too much."
She reaches down to stop you, or at least to slow you down enough that she can have half a second to breathe, but you slap her hand away and add your other hand to the mix, pumping with both hands, each changing its rhythm and pressure.
"Oh, fuck, fuck, fuck, fuck!" she says, "Too much! Too much! Gonna cum! Gonna cum!"