Need advise on creating paint strokes with motion 2...

i know this can be done with motion3 with ease. but don't have it yet.
since i am still using G4, and color will not work on my machine (at least based on Apple's system requirement), so i don't want to invest in the whole package just yet.

So i am trying to make a simple stroke/ write on effect.

I make the strokes in photoshop then import the image file to motion, then keyframe masks to reveal the image. Two problems thou 1. Sometimes it doesn't look natural, since I don't want to spend a lot of time keyframing it. 2 this is the weirdest. when i keyframe the shape of the mask, it sort of becomes a shape, meaning the mask all of sudden becomes a solid shape.
I suspect that i am doing this the dumb way; some people mentioned that they could use particle emmiter on a motion path to achieve the effect, but i couldn't.

please help me with some suggestions.

Thanks

Here's a way to do it using the replicator:

[www.motionsmarts.com]

thanks for the fast respond and the tutorial.

another question thou - the brush stroke that i am trying to create have uneven thickness, can i do that with replicator? if not any other suggestions?