question about how to remove oil from the bilge

It is a long story, but a bad service caused 5 quarts of oil to be dumped into my bilge. The people that serviced it made things right and cleaned the bilge, but did not get all the oil out. Anyone have any suggesions. I thought about putting some dish detergent in with some clean water and just let it slosh around each weekend and then drain until I am no longer seeing oil on the water coming out of the bilge.

Thanks