It will take you 20yrs to polish that with a dremel. You need several different grits to get aluminum to a polished state. It's hard, dirty work. I did it to some rims and I wont do it again. Mag masters does a good job (but bad customer service)
I would search google for how to videos
heres eastwoods product page
http://www.eastwoodco.com/jump.jsp?itemType=CATEGORY&itemID=432