This is how I do it with my pressure washer for antique, modern or farm equip where engine is not removed. For any part that I do not want water to get to in quantity I use heavy clear plastic like you buy by the roll at Lowe's, Home Depot etc usually in 10' X 50' rolls I cut a piece about 7-8' long then unfold it to the 10' wide width and for an A I snake it between the trans and body cutting the plastic to get around the shifter, pedals etc, up the firewall behind the motor. You have to work around the wires or better yet disconnect them. I put a ZIP close large bags over the distributor and another over the carb. and depending on fit sometimes use a zip tie as well to close the bag. I disconnect some of the rods to allow easier placement. and wrap the generator and starter as well, duct tape is your friend in securing the plastic. I drape another piece of plastic over the frame rails and over the fenders. Where I use more plastic, I tape the plastic together with duct tape, not touching the paint. I also put a piece between the radiator and motor extending out over the fenders and headlights and horn. It is a bit of a pain to do but really works great. I also use welding magnets to hold the plastic to the fenders, and those SS dishes with magnets to hold parts like you get at Harbor Freight also work good. I have hood holders on my A's which get it up high and out of the way. Finally I use plastic to keep the spray off the windshield and body. I run a line from my Hot Water heater, and some Simple Green in the washer and your good to go. Be careful when spraying where you put the water, I also start with lower pressure nozzles. After I do the engine bay and trans, I shut off the detergent and wash it all down with only hot water. I then remove the plastic and then wash the car at least 2 times to remove any of the de greaser that might of splashed somewhere.. I guarantee that you will get wet doing this, so summer time is best.