Two fingers in the front, two in the back.

You want more in your ass, so you pull your finger out of it so you can lube it up a little. You suck and lick your pointer and middle finger, shivering a bit at the taste of your ass, then stick those two fingers in your pussy to get plenty of wetness. Then you shove your pointer finger back in, which is much easier now, and slowly ease in your middle finger. You soon get into a good rhythm of fucking. As you slam into your pussy, you pull out of your ass, and vice versa. Your moans fill the cell.