I prefer my engine compartment cleaning wand that goes on the air compressor and I sue a product like TSP and water with it. If doing by hand then I would suggest something like simple green and lots of sponges. You would have to hose it down afterwards. One good tip I can offer is that even though alot of folks wrap their electrical parts in plastic and tape them up, it has been my experience that aluminum foil is much easier to work with and shape around the parts and protects just as well.