(Puts on Professor Glasses)
Ah, when she has a mouthful of cum, you can move your mouse to the Left, so she is off the penis, then Up, and she will tilt her head back. This keeps her from having the cum run out of her mouth onto her breasts (or the floor), and gets her to Swallow it.
Simple enough, really.
(Removes glasses, and fades into the background)