Coffee grounds will help neutralize odors, but you have to get rid of the diesel for it to help much. Using Dawn or some other strong dishwashing detergent will help get rid of the remaining diesel contaminating the bilge.
Servicemaster is a nationwide company that specializes in cleaning residences and commercial buildings. They have a product they use on heating oil spills that will do the trick for you and they'll sell it to you. Failing that, check with any company that does flood/fire damage restorations for the same product.