"Fingers" sound like a sand filter???

Your right, you can clean the oil's off with TSP or even dishwasher detergent. This is the powder, the kind you use in a dishwasher machine! Where I live dishwasher detergent (Costco) is a little less expensive than TSP (Home Depot, Lowes). After degreasing you will want to acid wash too.

Follow the dissassembly instructions in the filter's manual. If you don't have it sometimes the manufacturer has a manual you can download. There may be cleaning instructions in there also. If so follow them, if not I have done the following:

1. Degrease:
In big plastic garbage can soak the parts (degreasing is most important for the grids) for at least one hour, over night is most effective, in one cup trisodium phosphate (TSP) to five gallons water; or one cup dishwasher detergent to five gallons of water. A plastic garbage can that is tall enough to completely submerge the grids is good. Rinse before proceeding to the next step. WARNING: Failure to remove all oils and cleaning solution before acid soaking will result in a permanent restriction of water flow and cause premature failure. This is meant for filter cartridges but the same applies to DE grids.

2. Acid wash:
If the parts have a coating of algae, calcium carbonate (residue from calcium hypochlorite), iron, or other minerals, soak the cartridge in a solution of one part muriatic acid to twenty parts water until all bubbling stops. I usually just let em soak overnight. You can use the same garbage can as above, just empty the degreasing solution first in an appropriate place (sink, toilet, etc.) and rinse it out. When your done with the acid wash, do the same thing.