I do the top portion with a can of degreaser from local auto zone, had good luck with the citrus stuff. for the underside I take my car ramps to the power wash. Pull her up on the ramps and then I use the car wash degreaser stuff and let it set for about 5 to 10 mins. While I am waiting I suit up in my rain suit and once I've waited I blast away. The underside is the worst. I usually do this early Sat morning cause you get some weird looks being at a car wash with a rain suit on. I read or seen somewhere not to get it steam cleaned. Due to the steam getting into connectors and causing corrosion. I think it was ABC news or something. Good luck