WD 40 has kerosene which acts as a lubricant and short term protectant. I have always used the red scotchbrite with any cheap liquid dish soap and water mix. Just enough soap to foam up the water/soap mix, the soap is the lubricant. Works just like when you wet sand you use water.
The soap also removes oils and other contaminates.
When you are done and you want the satin look but also want corrosion protection use Alodine 1001 from any good paint shop. It is an invisible conversion coating (chromium etch) that protects the bare aluminum. It has been used in the aircraft industry for years and is easy to work with. Just follow the directions, the great thing is any time later you need to touch up the aluminum you can. Just get out the scotchbrite and repeat the process.
