It sounds like you are trying to recreate the look of bad compositing, which can be a combination of many things. Here are a few thoughts/ things to consider:
- Poor / improper lighting across a surface: this can be hard to do on deferred rendering
- Improper frame rate: This is difficult to do on particles without rewriting the particle motion system. It’s easier with skeletal meshes; just use stepped animation curves
- Improper or lack of shadowing: Lack of shadows is easy, simply turn them off. Improper shadowing (as if they were hand animated in the 70’s) is more difficult.
- Lack of motion blur: difficult to do on an object-by-object basis; not supported