Erase Vector Drawing?

programming flash
1

I have a Sprite that I draw into using lineTo. Later the sprite is drawn into a bitmap to add to a mask. That works great. The issue is erasing the vectors in the Sprite once they are drawn.

To draw I just do something like:
userDrawing.graphics.lineStyle(12,0x000000,1);
userDrawing.graphics.lineTo(mouseX,mouseY)

Figured it would be as simple as setting lineStyle like:
userDrawing.graphics.lineStyle(12,0x000000,0);
or
userDrawing.graphics.lineStyle(12,0x00000000,1);

But neither of those affect the lines already drawn.