You start stroking wildly, but she stops you and says:
"Not so fast!"
You slow down, but as she starts to remove her top, you get more excited and your stroking speeds up. Then she says:
"Just press it with the flat of your hand, and move in a circular motion, like I taught you!"
You slowly rub your cock against your stomach, and with each circle, your hand stretches the skin around the tip, causing a bit of pre-cum to leak out.