Bitmap drawing tool?

Anyone know the best way in Flash 8 to draw to bitmap surface when the user draws with the mouse, I want a chunky aliased circle, for example in Processing you would do:
strokeWeight(8);
line(mouseX, mouseY, pmouseX, pmouseY);

So is the best way in flash using some sort of set or copy pixels method or is it drawing a vector line and then adding it to the bitmap canvas.