I've had great luck with a diesel fired hot water pressure washer. Since not everybody has access to one (I got lucky as a local farmer has one for washing his equipment and truck and I have pulled him out of ditches so I get free use), a scrub brush, degreaser, and a regular pressure washer will work. For those that don't have access to that, a garden hose with a spray nozzle will work. Each type has it's own level of "elbow grease". The garden hose method will require much more manual scrubbing to remove the heavy grease. The best thing to do is scrub/scrape as much off manually as you can, then soak in degreaser followed up by spraying with the hose. It may take several repeat cycles to get into the nooks and crannies. If you want to paint when you are done, brake cleaner works well for final degreasing/prep. I'm also one that buys it by the case as it has several applications (cleaning brakes, degreasing before paint, wasp/hornet killer, etc.).
