I had this idea when I was doodling on ArtRage. I'm not sure if it's been posted before.
Step 1: Make another layer, above your background.
Step 2: Take any colour of glitter, any shape or size.
Step 3: Cover the whole layer with glitter. (The one above your background.
Step 4: Make another layer, above the glitter one.
Step 5: PAINT!
You can make your own personal paper grains with this technique.
You can make it look bubbly, leafy, or totally random.
Useful for abstract paintings.
You can make just small sections grainy if you want.
And of course, here's one I did earlier!