My favorite way to do this is actually using the local DIY carwash.
I grab some walmart shopping bags, rags, a wire brush, any can of engine degreaser. If you want to get a nice shine out of any chrome bling or polished/painted parts then choose your detailing tools and chemicals you need.
I place the shopping bags securely over electrical components, such as the fuse boxes, alternator, anywhere water can get into the engine such as the intake inlets, or over the filter of a CAI etc.
Spray on the degreaser on a warm motor, let it sit. If you want, start scrubbing the real grimy areas while the rest soaks.
After a good soak, start spraying. Not to your standard? Repeat. Too easy.
I need a job and a life.