FP10 provides the Vector datatype and command methods to make use of them. Intermixing .drawPath() with .lineTo() calls, sucked. It's possible my approach of calling drawPath with subsequent lineTos and moveTos was done entirely wrong. In any case sticking to drawPath exclusively for path commands seemed more maintainable.
_ http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/display/Graphics.html#drawPath()

With rudimentary moveTo / lineTo methods
point_commands = VECTOR
point_coordinates = VECTOR
foo.graphics.beginFill
foo.graphics.lineStyle
foo.graphics.drawPath(point_commands, point_coordinates)
foo.graphics.moveTo(a, b)
foo.graphics.lineTo(x, y)
foo.graphics.endFill

Replace by pushing Vectors.
...
point_commands.push(1)
point_coordinates.push(a, b)
point_commands.push(2)
point_coordinates.push(x, y)
foo.graphics.drawPath(point_commands, point_coordinates)
...