I usually use the engine degreaser GUNK or whatever one foams up and doesnt harm electrics or plastics . After I let that sit for a moment I pressure wash off the dirt, grime or dust off. Then after that I use towels to dry it off to make shure water doesnt get on anything that it doesnt need to and dry up. This process is only used if the engine bay is really dirty. But when i touch up I use dove soap, with a moderatley wet towel.