Drawing Application - Brushes

Hey,

Im creating a multiplayer drawing-game with Flash CS3 (AS3).
Basicly im creating a Shape-object and let the users draw freehand on this
with lineTo-commands. (Which coordinates is broadcasted.)

Now I want to enable different brushes and im not sure howto do this…
One thing ive tried is to apply filters like **blur **on the shape-object,
to create an illusion of a wet or soft brush.

But this cant be the solution because then noone can use different brushes in
same drawing.

Can anyone give me some hints howto solve it? Ive seen this on many sites where
the brushes are like watercolor, and gets smaller the more you draw…

Thanks.