If you have regularly cleaned your cartridges as needed and not let algae build in your pool, Filter Blaster is a quick way to get them cleaner than just water. Be aware that most cartridge manufacturers will recommend that you NOT soak in a acid solution unless you are sure all the organics and oils are off the material first. The acid will react with the oils and form an un-removable film, shortening the life of the cartridge.
Over-night soaking is the best way to get cartridges, and DE grids, clean if the right solution is used. There are some very good commercially available cleaners. You can also use a solution of dishwasher detergent (Cascade, not Dawn), or real TSP to soak in. After these remove the oils, a cleaning with an acid solution can be done if needed. Remember to rinse very well or you can end up with a lot of foam in your pool.