You will need one (1) beautiful assistant. Have the new switch ready with its new copper sealing washer in place. Both hands ready. Remove the old switch with one hand and block the port with the other hand's thumb. Now, quickly, fit the new one but only snug it up. Have your BA press on the brakes, crack the switch back loose and then tighten it up when only clear fluid is coming out. If you're slick, that will be it.