If you’re trying to create a single stroke (outline, contour) over several sprites or movieClips, you can simply create a parent object to hold them and apply a glow filter to it. In this example (yeah, it’s an old and basic as2 thing, a test I did ages ago) I applied a glow filter of 2 pixels Blur to the comic balloon background.
The background is made of two movieClips, each has it’s own behavior, if you click the horn you can adjust its size and direction, if you click the text area you can scale the textField and the balloon background along with it.
This trick can be really handy if you’re making animations of moving silhouettes. In this flash I used GreenSock’s TransformManager to make the textField and horn controlable.