A couple of things to consider if you plan on using a coin op sprayer.
1.) Your exhaust system (manifold) is hot (200F). Spraying colder water on it can cause it to contract rapidly and crack. So, wait a good amount of time before you spray. Maybe as long as it takes to touch the manifold, even.
2.) Distributor caps are not water proof. Get moisture inside and you will push the car out of the stall and you'll be looking for cloth to dry the underside of the cap out.
3.) I wouldn't spray much at the spark plug / wire connections for the same moisture reason.
Summary: Spraying metal parts is fine, as long as the temperature has cooled enough, try not to spray wires.