[jrow]

Hopefully I can straighten this out.

The compounds are based on the grit size. With Emory having the coarsest grit and white having the finest grit. The next coarsest would be Stainless Steel, then Tripoli.
What to use on what? Good question! You can use any compound to polish any metal within reason. The softer the metal the finer grit compound that you would use. This would also apply to the buffing wheels that you use the harder the metal the coarser the wheel. In this order; Sisal, Airway, Sewn, Loose and maybe Canton for brass and silver. You also must consider whether the buff is treated or not, which will make it cut better, and should last longer.
Aluminum comes in many hardnesses so you have to experiment and see what will work the best for your particular project.
Emory compound is about 400 grit so I wouldn't sand with anything finer than that before I start to polish.
Greaseless: Start with the finest that you can get, 320, if thats not doing the job within a reasonable amount of time and effort use the next coarsest ETC.
Wet sand or dry sand: Yes, both depending on what you are doing and how easy it is to get into the area that you are trying to sand. If I'm using a flap wheel, obviously I don't wet it, try grinders grease. I wet sand as much as possible using a little Dawn dish washing liquid in water to lubricate the metal. I clean my metal with Acetone/brake cleaner when I change buffing compounds or greaseless compounds. I also wash with Dawn and hot water when needed. The Dawn cuts the greasy compound real easy.
Change buffing wheel when you change compounds, rake often and don't load to much polish on your wheels.
Anyone that polishes has their own way to do things, this is the way I do mine. Hope it helps.

Questions?

John