I like using the store bought engine degreaser on the area around the exhaust manifold side of the engine. Also along the top of the intake manifold gasket before replacing it. I do small bursts of full strength pressure at the self serve car wash while using the lower pressure by squeezing the handle just slightly. Cover the distributor with multiple plastic bags. I also cover the wiring near the battery/coil/25 amp fuse. I really don't even spray that area around the AMM. Mainly just the cam cover, exhaust side of the engine, the engine crossmember both near the oil filter and from the front with the power steering rack. The oil pan and transmission are a bit hard to spray down with the can so I'll use a rag and pb blaster while I'm working under neath the car.