I use a grain bag inside a 10-gallon cooler with a bazooka in the bottom. Yeah, I know that's more complicated than necessary, but the system just sorta' grew. I used to make a mess trying to clean out the cooler in the laundry room. With the bag I can pull out the grain and dump the spent grain into a trash bag without making a mess. It works well. The bazooka maintains enough space between the bottom of the cooler and the bag, so the wort flows easily.
The bag does not make the system work better, it just allows easy clean up.