The PowerBall Mini and PowerCone used with a good metal polish can make the easy-to-access components a breeze. You run these at fairly low speeds with a cordless drill so as to not cause slinging, and they're pretty easy to use under the hood. Some areas you may have to do by hand with a towel, but the cone really gets into some tight spots.
If they're badly oxidized, you might start with something like Mag & Aluminum Polish, and follow with Billet Polish.
Work an area to create a black residue and keep working it. Gently wipe with a clean towel to see how your progress is coming along, and start on the next area doing the same thing.
Wash the ball or cone between products, and after use.
