Acetone will not really remove any oxides, it does degrease and carries away most residues. The stainless brushing is what removes the oxides. There are chemical oxide removers but as you noticed, most leave behind something that will still require a wipe down with acetone before welding. Aluminum will oxide instantly upon contact with air, so what you are doing is making the oxide layer as thin as possible. A lot depends on the size of the part and access. Sometimes chemical cleaning is an acceptable choice, and other times mechanical removal is prefered. Here is a cheap source of a great oxide remover, that is water rinsable and leaves minimal residue. An acetone wipedown is nice, but you can weld fine with just a rinse and dry, as well. Of course there are downsides like anything else. In this case it is that this is acid based (Hydrofluoric & Phosphoric) and produces some fumes, also while it will remove some grease and oil, since it is water based, really dirty parts should be degreased first for best results. At $20 a gallon it lasts a long time as you tend to dilute it quite a bit. I find about 10 to 1 in a spray bottle works great for aluminum that has been outside. Up to full strength for marine stuff like old boat props. The good thing about chemical cleaning is that it will penetrate porous castings and other places where a brush won't reach. It really makes a big difference in what boils out from something during the welding process.

http://www.grainger.com/Grainger/COM...-Cleaner-4PDA3

You can also get this at most any HVAC warehouse. There are a lot of brands, but they are always pink. There are also blue alkaline versions and soap versions, but they do not work as well, for this application.