I'm not against jet washing an engine bay of a Renault 4 - or any other car of its era. Water getting into any low tension electrical component (fusebox, alternator etc.) will dry long before it causes any trouble. It's moisture on any ignition component that will not allow the car to start. No matter how well you cover these components, moisture will get in, that's why I have found it's pointless to waste your time protecting them.
I jet wash the engine bay without taking any particular care - water can't get in carburettor from air filter cover. After I'm done, I never attempt to start the engine. I take off distributor cap and blow dry the internal parts, then wipe the contact points dry with kitchen towel. Then I remove ignition leads one by one and blow both ends dry, and spray them lightly with silicone spray, not forgetting their sockets on the distributor cap, and also ignition coil top.
10 out of 10 times the car will start instantly after applying this technique. Skip a step, or rush it, and you'll lose all day trying to start it.