I was thinking that it might be a future feature to wait for… but using particles is an excelent idea! I never thought about that. I found a work around for what I was tring to do any way. I wanted to be able to paint on layers and have it look like an acutal brush did it. What I ended up doing was making a bunch of randum induvidual paint stroke pictures in Photoshop (White on black). Then used Render-Stroke in AE to animate the stroke of the bursh with reveal image turned on. Composed all the brush strokes in a precomp and used that precomp as a track matte on my images.
Gave me the exact result I was looking for.
Thanks for your suggestions
Presto