There was a woman on Simply quilts who did it a neat way. She layered her top with batting or a piece of fleece. She then quilted around the area she wanted to be trapuntoed with water soluable thread. Next she cut away all of the excess batting/fleece and then layered the top,batting and back as usual. She then quilted it. The areas with double batting created a fantastic trapunto effect with no slits or whip stitching.