The Grain (Film Grain) effect in After Effects can make your work look awesome, there's just one problem, it takes forever to render or preview. Here's a hacky workaround that works best for mograph art. It freezes the grain, so it doesn't have to render a new version on each frame.
1. Make a new solid. 50% gray.
2. Put your grain effect on it.
3. Posterize time down to 0 fps.
4. Choose mode: overlay