Spraying 'paint' over an area - how to?

I want to simulate spraying paint over a flat area, is it possible to do this with Construct 2?

For example, you'll hold down the mouse and as you move over the white area the spray can will spray colored paint over the area. When it's all covered up, level complete. Is it possible to create this and most importantly - how? Is it difficult?

I think I'll need some sort of masking effect, like Flash has.

Thanks!

This is how i would do it....

I would do the "Spray" by creating sprites where the mouse points each tick.

To know if the whole area where covered i would have a grid of sprites cover the area, and when a "spray" sprite would touch one of the grid sprites it would remove the grid sprite. When no grid sprites are left, you are done.