There's an excellent product called De-Solv-It. It used to be readily available at the big stores, but still can be ordered direct from the manufacturer. It's one of those orange envio-friendly very low viscosity liquids. A light spray on the filthy areas (including really greasy tools), let it set five minutes, and hose it off. Not harmful to aluminum or magnesium. Does not easly evaporate, so must be rinsed or wiped off. Great for greasy/slimey household chores, too.
