I've just constructed a file in Illustrator for placing stars on the digital painting "The Apprentice".
This is a screen capture of a segment of my work area. I've toggled from Preview (which shows the art as it will be rendered out) to Artwork (which shows the "skeletons" underlying all the various shapes.
Scatter effects look simple but they're very sensitive. Placing each spark one by one is too costly in time. What's needed is a vector program.
First I made one star using vectors. There are three layers to it. The bottom layer has six points and is yellow. The next layer is a slightly smaller six-pointed star. The third layer is a pure white circle.
Notice that these stars aren't showing up in this picture, however. Only their Path, which is like a wire upon which they're hung, can be seen.
I capture the first star, make it a Group, then drag it onto the Brushes palette. I make it a Scatter brush. Now I can paint lines that are invisible, but numerous stars are "attached" to it.
One of the most valuable features of Illustrator is its interpolation effect, where I can draw *near* the line on which I am working, and the program shifts it over to the new location. If I don't like a swoosh or swoop, I draw it again.
Knowing I'm going to want some stars to be more faint, I use three layers. Later, I'll make the starry layers very slightly transparent.
When this file is Exported as a .PSD (Photo Shop), it has five layers: three layers of different-sized stars, one layer with the Apprentice image, and one layer that's a plain white rectangle background, which I can ditch.
Now I can blur, motion-blur, soften my sparks. I can duplicate a layer and give it really soft Gaussian blur for a pleasant glow.