I sometimes go to the carwash and use Gunk, carb cleaner, simple green, or a mix with the high pressure washer. Often you can leave the wand on the low setting for work close to electronics. Better to do this on TWO seperate days since the 2nd time can get parts you missed without blasting the h... out of everything the first time to do a final and complete job. Of course bagging electronics, distributor, alternator, etc. is nice. BTW, some folks use spray pledge to shine after dry, others spray lacquer on metal, armorall on rubber. A truck supply house has 1 pint cans of connector grease for under $5, this packs the connectors to waterproof after spray cleaning with electronic cleaner suitable for plastic. Your car came with grease in connectors. HOWEVER, DISCONNECTING THE CONNECTORS MAY CAUSE BREAKAGE at the connector, so if unsure don't unplug.

what I really want is to find a steam cleaning source, like better used car dealers use. Less water pressure, hot water and steam, produce a better overall result but cost $$$. I know people who steam clean their tractors, etc. but don't do other peoples.
finally, if at car wash, after spraying immediately remove bags and START ENGINE. Water can drip into ignition areas and stop car so an immediate start helps to dry out before drip in. Just FYI