Before and after
My potion of choice - Gtechniq W5 All Purpose Cleaner, and a soft brush. This gets most of the dirt off and is just rinsed off with water. I use brake cleaner for the real heavy grease and oil (mostly on the other side), and I'm now also using Elbow Grease for lighter oily dirt. Elbow Grease is ok on heavy stuff if you use a stiff brush, but on paint I prefer to use the brake cleaner as it just dissolves it with much less effort and reduces the risk of scratches.
After the various cleaning solutions, I blow it dry with compressed air, then go over with quick detailer to pick up the last of the smears.
Almost there now. I need to deal with the snapped fasteners, and clean out the wheel arches, then I'll go over the whole lot with sealant to make it hydrophobic.
